Outer diameter 1. Standard diameters of steel pipes. Nominal pipe diameter Dy. mm

The most important parameters of pipe products are pipe diameters in inches and millimeters. Many property owners are faced with the need to replace the piping system and, accordingly, the search for the required materials. High-quality assembly can be ensured provided that the diameter of the pipe and the dimensions of the connecting elements match.

Dimensional designations of modern types of pipes

When choosing the necessary products, regardless of what material they are made of, a number of indicators should be taken into account:

1. Outer diameter (Dн) in millimeters. The main characteristic of pipes. The sum of the internal section of the pipe and twice the wall thickness is the external parameter.
2. Inner diameter (working section) in millimeters. This parameter is of great importance for determining the patency of the system. To find out, it is necessary to subtract twice the size of the pipe wall thickness from the outer diameter.
3. Wall thickness in millimeters (S). The quality of pipe products - its volume and strength - depends on this parameter. It is calculated as the difference between the values ​​of the outer and inner sections of the pipe.
4. Nominal passage in millimeters, marked as Dу. It is the average value of the inner diameter, which is rounded up to the standard parameter. This size is taken into account when choosing the appropriate fittings and fittings.
5. Nominal diameter in inches. This concept was introduced to standardize the labeling of products made from different materials. The value is equal to the nominal bore (read also: “What is the nominal diameter of the pipe? Norms and standards”). This parameter allows you to select products made from different types of raw materials when combining them in the system. The fact is that pipe sizes in inches are indicated on steel pipe products, but copper and aluminum are marked in millimeters. Inch values ​​must be rounded up.

Measuring systems for pipes

There are two methods of measurement, the emergence of which has historical roots:

• imperial system- expressed in inches. Currently, it is used exclusively for water and gas pipes made of steel and fittings for arranging water mains;
• metric system has the following units of measurement - millimeters, centimeters, meters. It is used for all other types of pipe products.

In the case of joining pipelines made of different materials, there are difficulties in converting to millimeters and vice versa. An ordinary inch is equal to 25.4 millimeters - it is used to measure the diameter of the inner. But there is also a special unit of measurement - this is a pipe inch, which is 33.249 millimeters. Its peculiarity is explained by the fact that it includes the inner diameter and the thickness of two walls. The exception is the ½ inch conduit.

Differences between metric and inch systems of measurement

Visually, it will not be difficult to distinguish an inch pipe from a metric one. To do this, just look at the threads of the thread. At the same time, it is almost impossible to notice the difference in degrees between the turns with the naked eye, since for an inch product it is 55, and for a metric product it is 60. But it is almost impossible not to see that a one-inch pipe has rounded threads.

To measure the thread pitch, you can use a special device called a thread gauge, but if it is not available, a regular school ruler or any other measuring device will do.

Metric pipes are measured only along the outer boundaries of the threads, and inch pipes are measured exclusively along the inner surface. To find out the pipe size in inches and mm,

one should use the imperial or metric system of measurement, each of which is currently in demand.

Converting inch sizes to metric sizes

If necessary, you can use the special reference literature containing the relevant tables. For example, in GOST, which regulates the parameters of the VGP, there are values ​​​​of both an inch conditional transition and a millimeter one.

So, if you use the table, it becomes clear that the dimensions of the inch pipe will not be equal to 25.4 millimeters. Conditional passage - will be 25 millimeters with an outer diameter of -33.6 millimeters.

The most convenient table contains the nominal bore of the pipe, expressed in inches, its external size and the equivalent diameter in millimeters. It corresponds to the inch bandwidth. So a steel pipeline section of 1 inch can be connected to a polyethylene product, in which the conditional passage is 25 millimeters.

What is the size of inch pipes in mm?

In the construction market, 2 sizes of structures are popular:

• 1\2 and 3\4 - make up a separate category. due to special thread parameters (1.814), per 1 unit. measures accounted for 14 strands;
• within 1 - 6 inches, the pitch is reduced to 2.309, forming 11 threads that do not affect the decrease or increase in the quality of the connection.

One inch is 25.4 mm long, it is used to determine the internal parameters, but when laying reinforced pipes, the diameter is 33.249 mm (including the internal section and 2 walls). There is an exception in the range of steel structures - products in ½ inch, where the outer section is 21.25 mm. This parameter is used when calculating the dimensions of pipes with cylindrical threads. When calculating for pipes with a cross section of 5 inches, the internal dimension will be 12.7 cm, and the external - 166.245 (reduced to 1 decimal place is allowed).

The difference between measurement systems

In terms of external parameters, inch designs do not differ from metric ones, the difference lies in the type of notches. There are 2 types of threads according to the inch system - English and American. The first option corresponds to a notch angle of 55 degrees, and the metric (American) system with an angle of 60 degrees. generally accepted.

At different degrees, it is difficult to distinguish the angle by 55 - for inch and 60 - for metric designs, and the rounding of the threads is immediately visible, the occurrence of an error is impossible. A thread gauge is used to measure the thread pitch, but an ordinary ruler or other device is well used instead.

Replacing steel pipes with polymer ones

In the gas and water supply network, steel products are used, the diameter of which is indicated in inches (1″, 2″) or fractions (1/2″, 3/4″). When measuring the cross section of the pipe 1″, the result will be 33.5 mm, which corresponds to 1″ (25.4 mm). When arranging pipeline reinforcing elements, where the parameters are indicated in inches, there are no difficulties. But when installing products made of PP, copper or stainless steel instead of steel structures, it is required to take into account the difference in the name and parameters.

To create a given level of flow, the internal diameter of the pipes is taken into account. For inch ordinary pipes, it is 27.1 mm, for reinforced 25.5 mm, closest to 1 ″. Pipelines are designated in conventional units of the flow area Du (DN). It determines the parameters of the pipe clearance and is indicated in numerical values. The step of the conditional flow section is selected taking into account the increase in throughput characteristics by 40-60% with an increase in the index. If the external cross-section and the purpose of the structures are known, the internal cross-section is determined using the dimension table.

In the process of connecting steel pipes with polymer structures, replacing one with another, conventional adapters are used. Dimensional mismatch results from the use of copper, aluminum or stainless steel products manufactured to metric standards. The actual metric dimensions of the pipes are taken into account - internal and external.

Steel pipes of the Russian Federation in comparison with the European standard

To compare the range of pipes according to GOST RF and European standards, the following table is used:

How to decide on the choice of diameter?

Their throughput characteristics depend on the diameter of water pipes - the volume of water passed for 1 unit. time. It depends on the speed of the water flow. With its increase, the risk of pressure drop in the line increases. Throughput characteristics are calculated according to formulas, but when planning intra-apartment wiring, they take pipes of certain parameters.

For the plumbing system:

For the riser, structures with an internal cross section are used:

Given that the internal cross section of half-inch polymer pipes varies from 11 to 13 mm, and one-inch pipes from 21 to 23, an experienced plumber will be able to determine the exact parameters when replacing. With a complex type of wiring, numerous joints, turns and laying the network at a great distance, reducing the pressure, it should be possible to carry out the wiring of pipes with a large cross section. As the diameter increases, the pressure level increases.

Below is a table for determining the patency of steel pipes:

Steel pipe diameter

The cross section of the pipes corresponds to a number of indicators:

• Nominal diameter (Dn, Dy) - nominal parameters (in mm) of the internal cross-section of pipes or their rounded indicators, in inches.
• Rated value (Dn Dn,).
• external size. The metric calculation system allows classifying structures into small ones - from 5 ... 102 mm, medium - from 102 ... 426, large - 426 mm and more.
• Wall thickness.
• inner diameter.

The internal cross section of pipes with different threads corresponds to the following parameters:

• 1/2 inch pipeline - 1.27 cm;
• 3/4 inch - 1.9 cm;
• 7/8 inch - 2.22 cm;
• 1 inch - 2.54 cm;
• 1.5 inches - 3.81 cm;
• 2 inches - 5.08 cm.

The following indicators are used to determine the thread diameter:

• pipeline 1/2 inch - 2.04 - 2.07 cm;
• 3/4 inches - 2.59 - 2.62 cm;
• 7/8 inch - 2.99 - 3 cm;
• 1 inch - 3.27 - 3.3 cm;
• 1.5 inches - 4.58 - 4.62 cm;
• 2 inches - 5.79 - 5.83 cm.

Table of correspondence between the diameter of steel pipes and polymer structures:

Steel pipe prices:

Pipe diameter PP

PP pipes are produced with a diameter of 0.5 to 40 cm or more. The diameter is internal and external. The first indicator allows you to find out the volume of environments traversed in 1 unit. time. The external cross section is used for construction calculations, namely the choice of a niche or pit for laying a highway. External parameters allow you to choose the right fittings with the corresponding internal indicators.

• Small - 0.5; one; 1.5; 2; 2.5; 3.2; four; 5; 6.3 and 7.5 cm is used for heating systems, drains and water supply in private buildings. An internal cross section of 3.2 cm is most popular in multi-storey buildings.
• Medium - 8; 9; ten; eleven; 12.5; 16; twenty; 25 and 31.5 cm is used for arranging water supply and sewer systems, allowing you to change cast iron products with similar external parameters. Internal dimensions of 8, 9 and 10 cm are ideal for chemical environments.
• Large - 40 cm or more is used for arranging cold water supply and ventilation systems.

Pipes are marked in inches and mm. When choosing structures for the plumbing and heating systems, the wall thickness is taken into account, which affects the conditional patency of highways with the same external parameters. With an increase in its parameter, an increase in pressure in the plumbing system is allowed. Small dimensions allow to reduce the level of costs for the purchase of material and water consumption.

Inch pipe - dimensions in mm and diameter

Inch pipe - dimensions (in mm), specifications and prices. Correspondence table of steel and plastic products for gas and water supply. The difference between GOST and European standards.

Pipe 1 inch - what diameter

It is impossible to mount a communication system of any kind in such a way as to completely avoid connections. If only because the pipeline is eventually brought to some kind of consumption object - plumbing, radiator, washing machine, and is connected to the outlet of the device. And the main condition for a sealed high-quality assembly is the correspondence between the diameter of the pipe and the size of the connecting element.

Dimensional parameters of the pipe

Regardless of the material of manufacture - polymer, metal, ceramics, and so on, the product is characterized by a number of indicators, based on which, the consumer can choose the necessary product.

• Outer diameter - that is, the outer size of the pipe (we are talking only about a circular section).
• Internal - the size of the working section.
• Wall thickness - largely determines the strength of the product.

The sum of the inner diameter and twice the wall thickness is the outer diameter. The actual state of affairs corresponds to this statement. But when it comes to VGP, it is necessary to take into account the following point. Most often, conduits are connected by a threaded method. The thread is applied to the outer part, as a result, the diameter of the thread is by no means equal to the outer size. And since it is important to know exactly the thread indicators for installation, this parameter turns out to be more important and is often indicated instead of the actual size of the product.

For example, a 1 inch conduit is not at all equal in outer diameter to 2.54 cm, since 1 inch is an indication of the size of the thread.

This confusion is exacerbated by the use of two measuring systems on the one hand, and the variety of products currently available on the other.

Conditional pass

The task of the plumbing system is to uniformly supply all consumers with the proper amount of water. The main calculation parameters are the throughput of the pipeline, that is, the amount of water that can pass per unit of time.

• This parameter is called conditional passage - Dn. It does not have a unit of measurement as such - it is a conditional, non-actual value, indicated in integers and indicates the approximate conditional clearance of the pipe. The step between the values ​​is calculated theoretically, with the condition that with each subsequent increase, the throughput of the pipeline increases by 40–60%.

The convenience of the system is obvious only in practical use. It is enough to select conduits and fittings with an equal conditional passage according to the table in order to guarantee a working plumbing system.

Accordingly, a 1 inch steel pipe has a nominal bore of 1 inch, while its actual inner diameter is 25.5 mm, the outer threaded one is 33, 25.

Measuring systems

The presence of two methods of measurement has historical roots.

• Imperial - in inches, today it is used only for water and gas steel pipes and related plumbing fittings.
• Metric - in mm, cm and m. Used for any other pipe products.

When joining conduits from different materials, difficulties arise with the recalculation from one system to another.

Inch and metric pipes

Both inch and standard steel conduits are produced, which further confuses the matter. You can visually distinguish them by the type of thread of the thread - a 1-inch pipe has rounded threads. The photos show samples.

Thread pitch is measured in different ways. In metric products, along the outer boundaries of the threads, in inch products, along the inner ones. The distance is different for different section sizes.

Pipe 1 inch, which is used in the imperial system, is not equal to 2.54 cm, as it should be, but equals 3.3249, since it includes both the internal dimension and the wall thickness. The exception is the ½ inch conduit.

Converting inch to metric sizes

The reference literature contains corresponding tables. The same GOST, which regulates the parameters of the VGP, indicates both an inch nominal bore and a millimeter one. Unfortunately, in order to assemble the system into one whole, the actual value of the inner diameter is also required. While the tables more often indicate the outer.

The most convenient table contains the nominal size in inches, the external size of the pipe and the equivalent diameter in mm. It indicates a bandwidth that corresponds to an inch.

For example, a 1 inch steel conduit can be connected to a polyethylene conduit, the conditional passage of which is 25 mm.

Steel pipe diameters

In practice, there are diameters: nominal, internal, external, conditional passage. The values ​​​​are indicated in the marking of pipes: for steel - in inches, for others - in millimeters. How to determine the diameter of a steel pipe in mm? This will help the tables of correspondence of the diameters of steel products.

Steel pipes with a diameter of 100 mm

The main characteristic of a steel pipe is its diameter. This parameter determines the purpose, length of the pipeline, composition and physical characteristics of the transported substance. All diameter values ​​are standardized and regulated by regulatory documents - standard sizes and requirements for products are regulated by GOST. Each type of pipe has its own standard.

What pipe diameters exist

Theoretically, the diameter of the pipe is quite simply added to the formulas when determining any values. In practice, everything is more complicated - they distinguish between outer, inner, nominal diameters, wall thickness. What are the terms and what do they mean?

1. Conditional passage - the internal size of the pipe, determined in millimeters. In inches requires rounding. It is used for the correct joining of two products, for example, a pipeline and a fitting.
2. The wall thickness of the pipe (S) is a physical quantity in millimeters, on which many quality indicators of the product depend, including permeability, volume. It is defined as the difference between the outer and inner diameters.
3. The inner diameter is a physical quantity in millimeters, an important parameter for determining the patency of the highway. Formula for calculation: Dvn=Dn-2S
4. Outer diameter (Dn) - has small dimensions (5 ... 102 mm), medium - 103 ... 426 mm, large - 427 mm or more.
5. nominal diameter - close by definition to the nominal diameter, but has more accurate values.

The numerical value of the diameters of steel pipes

A huge assortment of steel pipes for various purposes, designs, types is presented in the form of tables, where the main parameters are:

• conditional passage (or nominal diameter);
• outer diameter of the pipe;
• wall thickness.

Sometimes the weight of the product is entered into the steel pipe diameter table depending on its dimensions, as well as the parameters of the nominal diameter.

Tabular values ​​​​of steel pipe diameters

Tables are convenient to use when determining the exact dimensions of products when they are connected. For example, steel pipes are most often indicated in inches - this dimension is accepted in many parts of the world. While polymer products are usually measured in millimeters, which creates some difficulties when joining metal-plastic, cast-iron, copper pipes with steel pipes in the plumbing system. Diameter matching tables help determine the required dimensions of the connecting elements and connect them correctly.

In table 1, nominal diameters in mm correspond to certain values ​​​​of the inner diameter in inches. Pay attention to how the values ​​of the outer diameter differ for different types of pipes: seamless, electric-welded, metal-plastic. The difference can be up to 17 mm.

How to convert inches to millimeters correctly

Inch units are rounded up when converted to millimeters. Obviously, knowing the constant 1 inch is equal to 2.54 cm, you can independently calculate the diameter values ​​​​according to the metric dimension. But the problem is not how to calculate, but how to correctly determine the diameter. As practical measurements of steel pipes show, their marked diameter in inches does not correspond to the measured data in millimeters. That is, the size is 1 ”(respectively 25.4 mm), but in reality it turns out 33.5 mm. What is the reason for this discrepancy?

First of all, the inner diameter of the pipe is stamped in the designation. Secondly, the unit of measurement of the diameter is the dimension of the conditional passage (DN), which is indicated in integers. Moreover, the value of the size increases with the growth of the index (patency) of the pipe by 40-60% with each step. The conditional passage of the pipe corresponds to the internal clearance (nominal diameter) of the line, but an integer is taken as the final value, rounding the calculated one up. The conditional passage of the line is standardized according to GOST 355-52.

To correctly select the elements of gas and water pipes with inch markings, the best option would be to use tables. When connecting elements of a water and gas pipeline with metric and inch systems of measurement (for example, steel pipelines with products made of copper, brass, polypropylene), it is important to consider not only the inner, but also the outer diameter.

Standard sizes of steel pipes

The generally accepted standard values ​​for the inner diameter of steel pipes are determined next: 6, 10, 15, 20, 25, 32, 40, 50, 65, 80, 100, 110, etc. The conditional passage of the pipe, calculated in inches, when converted to the metric system, is just rounded up to the nearest parameter from the standard range.

The most commonly used pipes are from 426 to 1220 mm in diameter. These are lines for water, gas, sewer, irrigation systems.

For plumbing and heating in apartments of multi-storey and private buildings, pipes of small diameter are used. Medium-diameter steel products are used for risers in urban infrastructure, as well as in the oil industry. These are products with a diameter of ¾”, for wiring inside ½”.

According to the tables, the diameters of pipes made of plastic, copper, brass are similarly determined. The method of converting inch dimensions to metric is used when connecting products from different materials. In the presence of fittings, the installation of gas pipelines made of steel is simplified - these nuances are already taken into account in the connecting elements.

Diameters of steel pipes: table, dimensions in inches and millimeters, guests

In practice, there are diameters: nominal, internal, external, conditional passage. The values ​​​​are indicated in the marking of pipes: for steel - in inches, for others - in millimeters. How to determine the diameter of a steel pipe in mm? This will help the tables of correspondence of the diameters of steel products.

The main parameter characterizing a steel pipe is the diameter of an inch pipe. This characteristic indicates the scope of this pipe, the length of the pipeline, the composition and physical parameters of the substance transported through it. All diameter values ​​must comply with standardization regulations that relate to standard sizes, all requirements for these products are carefully regulated by GOST. Each type of pipe has its own standard.

Dimensions are indicated on the marking: for steel - in inches, for others - in millimeters. How to find out the diameter of a steel pipe in mm? Here tables of diameters of steel products will come to the rescue.

Diameter is not the only characteristic by which steel pipes differ, an equally important parameter is the method of their production, which is also a key point when choosing them.

1. Straight seam (electrowelded). For their production, sheet steel (strip) is used, which, with the help of special equipment, is bent to the required diameter, after which the edges are connected by welding. Welding work guarantees the minimum width of the seam, which allows the use of these products for the construction of water and gas mains. Most often, the material is carbon or low alloy steel. Finished product indicators are regulated by the following documents: GOST 10704-91, GOST 10705-80 GOST 10706-76.
2. It is necessary to pay attention to the fact that the pipe, which was made in accordance with the standard 10706-26, has increased strength among its own kind - after the first connecting seam has been made, it is additionally reinforced with two more from the inside and two from the outside. Regulations indicate the diameters of products made using electric welding. Their size ranges from 10 to 1420 mm.
3. Spiral-seam. For the manufacture of this type of product, steel in rolls is used. These products also have a seam, but compared to the previous type of product, it is wider, respectively, and the ability to withstand internal pressure for such pipes is lower. These products are used in the construction of gas pipeline systems. This type of pipe is regulated by GOST 8696-74.
4. Seamless. The manufacture of products of this type consists in the deformation of special steel blanks. Deformation is performed both with exposure to high temperatures and the cold method (GOST 8732-78, 8731-74 and GOST 8734-75, respectively). The absence of a seam is a positive reflection on strength - the internal pressure is evenly distributed over the walls (it has no "weak" places).

Regarding diameters, it is worth noting that regulations control their production up to a value of 250 mm. When purchasing products whose diameter is greater than the specified one, you only have to trust the integrity of the manufacturer.

It's important to know! If you need the most durable pipes, the best option would be to purchase a seamless deck molded product. The initial characteristics of the metal do not change due to the effects of temperature, which has a positive effect on strength.

Also, if the key requirement is the ability to withstand internal pressures, round-shaped products are most suitable for this role. Profile pipes are more resistant to mechanical stress (they are well suited for the manufacture of various kinds of frames, load-bearing structures).

What are the pipe diameters?

Theoretically, the diameter of the pipe is quite simply added to any calculations during the determination of certain values. But in reality, everything is much more complicated - there is a wall thickness, the diameter differs in nominal, internal and external. What concepts exist and their meaning:

1. Nominal passage - the internal size of the pipe, determined in millimeters. In inches, rounding is required. It is used for the correct joining of two products, for example, a pipe and a fitting.
2. Pipe wall thickness (S) - measured in millimeters, affects most of the quality characteristics, which include volume, permeability. It is defined as the difference between the outer and inner diameters.
3. The inner diameter - a physical quantity, determined in millimeters, plays a rather large role in determining the patency of the highway. Formula for calculation: Dvn=Dn-2S.
4. Outer diameter (DN) - small sizes - 5 ... 102 mm, medium - 103 ... 426, large - from 427 and above.
5. Nominal diameter - by definition, it stands next to the nominal diameter, but has a more accurate value.

A large assortment of steel pipes for various purposes, manufacture, types is presented in the form of tables. It happens that in the table of diameters of steel pipes, the values ​​\u200b\u200bof the masses of the product are entered depending on its dimensions, as well as the values ​​​​of the nominal diameter.

Inches or mm: where did the confusion come from?

Pipes whose diameter is defined in inches (1"", 2"") and/or fractions of an inch (½'', ¾"), the generally accepted standard for water and gas supply.

Pipes that are used for gas or water mains are usually measured in inches and not in millimeters. The inch diameter of the pipe is 33.5 mm (see table), but the SI inch is 24.4 mm. The thing is that the size of the pipes is determined by the inner diameter, and not by the outer diameter.

Measure a diameter of 1 '' (how to measure pipes is described below) and you will have a value of 33.5 mm, which of course will contradict the classic linear unit conversion table.

Usually installing inch pipes does not cause any problems. But during their replacement with plastic, copper or stainless steel, a problem arises - the discrepancy between the indicated inch value and its real value. Usually such a discrepancy is perplexing, but if you look deeper into the processes that occur in the pipe, then everything falls into place.

The whole point is that during the creation of a water flow, the main role is given to the inner, and not the outer diameter, and because of this, it is used as a designation. But the discrepancy with the usual designation system still remains, since the inner diameter of a conventional pipe is 27.1 mm, and that of a reinforced pipe is 25.5 mm. The latter is not far from the equality that one inch is equal to 25.4, but still it is not.

The thing is that pipes are designated by a nominal diameter, which is rounded up to a standard value (nominal diameter Dy).

Suppose the outer diameter of the pipe is 159 mm with a wall thickness of 7 mm, in this case the exact inner diameter will be the following value, which can be calculated using the formula D \u003d 159 - 7 * 2 \u003d 145 mm. With a wall thickness of 5 mm, the diameter will be 149 mm. But in both the first and second cases, the conditional passage will be the same and will be equal to 150 mm.

In cases with plastic pipes, transition elements are used to solve the problem of inappropriate sizes. If it is necessary to replace or join inch pipes with pipes that have real metric dimensions, made from materials such as aluminum, copper, stainless steel, both the inner and outer diameters must be taken into account.

Nominal bore table in inches:

Conventional diameter	inches	Conventional diameter	inches	Conventional diameter	inches
6	1/8"	150	6"	900	36"
8	¼"	175	7"	1000	40"
10	3/8"	200	8"	1050	42"
15	½"	225	9"	1100	44"
20	¾"	250	10"	1200	48"
25	1"	275	11"	1300	52"
32	1 (¼)"	300	12"	1400	56"
40	1 (½)"	350	14"	1500	60"
50	2"	400	16"	1600	64"
65	2(½)"	450	18"	1700	68"
80	3"	500	20"	1800	72"
90	3 (½)"	600	24"	1900	76"
100	4"	700	28"	2000	80"
125	5"	800	32"	2200	88"

The size of the nominal passage is selected in such a way that the throughput of the pipeline increases from 40 to 60%, depending on the increase in the index value.

Which pipes are considered small, medium, large?

Quite often, in many sources you can find a phrase like “We take any pipe of medium diameter ...”, but no one indicates the specific values ​​\u200b\u200bof this diameter. To understand this issue, you first need to decide on what diameter you need to build on: it can be both internal and external. The first is of great importance when calculating the transport characteristics of water or gas, and the second determines the ability to withstand mechanical loads.

External diameters:

• from 426 mm - large;
• 102-246 - medium;
• 5-102 - small.

If the conversation is about the inner diameter, then it is better to check with a special table.

Correspondence table for the diameter of the nominal bore, thread and outer diameters of the pipeline in inches and mm:

Nominal pipe diameter Dy. mm	Thread diameter G". inch	Outer pipe diameter Dn. mm
		Pipes steel water / gas pipeline GOST 3263-75	Pipes steel electrowelded longitudinal GOST 10704-91. Pipes steel seamless hot deformed GOST 8732-78. GOST 8731-74)	polymer pipe. PE, PP, PVC
10	3/8"	17	16	16
15	½"	21.3	20	20
20	¾"	26.8	26	25
25	1"	33.5	32	32
32	1¼"	42.3	42	40
40	1½"	48	45	50
50	2"	60	57	63
65	2½"	75.5	76	75
80	3"	88.5	89	90
90	3½"	101.3
100	4"	114	108	110
125	5"	140	133	125
150	6"	165	159	160
160	6½"		180	180
200			219	225
225			245	250
250			273	280
300			325	315
400			426	400
10	3/8"	17	16	16

GOST - state standard used in heat - gas - oil - pipelines
ISO - standard for designating diameters, used in plumbing engineering systems
SMS - Swedish standard for pipe and valve diameters
DIN / EN - the main European range for steel pipes according to DIN2448 / DIN2458
DU (Dy) - conditional pass.

How to measure pipe diameter?

Most often, during the acquisition, you can simply ask a consultant a question or look at the marking. But it happens that one of the communication systems needs repair and replacement of pipes, and it is not known what diameter the already installed pipes are. There are several ways to determine the diameter, but we will talk about the simplest:

Using a tape measure or centimeter tape, wrapping it around the pipe, write down the resulting value. Now, in order to find out the diameter, you need to divide the obtained data by the number Pi (3.1415).

Let's say that the pipe has a girth of 6 cm. Its diameter is calculated as follows: 6 x 3.1415 = 18.85 mm. After the outer diameter is obtained, the inner diameter can also be calculated. For this calculation, we need to know the wall thickness (if there is a cut, measure it with any measuring tool with a millimeter graduation). For example, the walls have a thickness of 1mm. This figure is multiplied by 2 (even with a thickness of 3 mm it is still multiplied by 2) and subtracted from the outer diameter.

As a sample, you can give the following calculation: (18.85- (2 x 1 mm) \u003d 16.85 mm).

Diameters and other characteristics of stainless steel pipe:

Pass, mm	Outer diameter, mm	Wall thickness, mm		Weight of 1 m pipe (kg)
		standard	reinforced	standard	reinforced
10	17	2.2	2.8	0.61	0.74
15	21.3	2.8	3.2	1.28	1.43
20	26.8	2.8	3.2	1.66	1.86
25	33.5	3.2	4	2.39	2.91
32	42.3	3.2	4	3.09	3.78
40	48	3.5	4	3.84	4.34
50	60	3.5	4.5	4.88	6.16
65	75.5	4	4.5	7.05	7.88
80	88.5	4	4.5	8.34	9.32
100	114	4.5	5	12.15	13.44
125	140	4.5	5.5	15.04	18.24
150	165	4.5	5.5	17.81	21.63

A very good help in this matter is the caliper. The pipe is simply wrapped around the measuring teeth and looked at the value obtained on the scale.

According to the tables, the diameters of plastic, brass and copper pipes are thus determined. The method of converting inch to metric is used when joining products made from different materials. In the case when there are fittings for gas or water pipes made of steel, installation becomes much easier - the connecting elements take this feature into account.

Diameter is one of the most important dimensional characteristics of steel pipes. Thanks to such a parameter as the diameter, all the necessary design calculations can be made.

Standard diameters of steel pipes are strictly regulated by GOST 10704-91.

Purely conditionally, pipe diameters are divided into the following categories:

- large diameter (more than 508 millimeters),

- medium diameter (114-530 millimeters)

- and small diameter (no more than 114 millimeters).

Main overall characteristics

It is according to these characteristics that the diameters of steel pipes are determined according to GOSTs and TUs:

• internal diameter of pipes;
• the outer diameter of the pipes - is their main overall characteristic according to GOSTs;
• conditional diameter of the pipe. Represents the nominal size of the inner diameter of the pipe;
• pipe wall thickness;
• nominal pipe diameter.

1. The classification of steel pipes into small, medium and large is made exactly according to the outer diameter (Dn). Standard diameters are shown in the table.
   
2. Most often, steel pipes of the following diameters are used: 426, 530, 159, 219, 720, 920, 273, 325, 1420 and 1220 millimeters.
3. The small outer diameter of steel pipes is used for the construction of plumbing systems in apartments, houses and other premises.
4. Medium-diameter steel pipes are used for the installation of municipal water pipes, as well as in field systems for collecting crude oil.
5. The largest diameter steel pipes are needed for the construction of main gas and oil pipelines.

Internal diameters of steel pipes

1. The inner diameter of steel pipes (Din) with a constant outer diameter can vary significantly. To standardize the diameter of pipes, a term such as "conditional passage (diameter)" is used. It is designated Dy.
2. Nominal bore is the rounded nominal size of the inner diameter. It always rounds up. The value of the nominal diameter of steel pipes is determined by GOST 355-52.
3. The inner diameter can be calculated using the following formula: Din = Dn - 2S.
4. Steel pipes have internal diameters: 6, 15, 10, 20, 25, 50, 65, 32, 40, 80, 100, 125, 200.

Steel pipe diameters in inches

In addition to millimeters, the diameter of steel pipes can also be measured in inches. One inch equals 25.4 millimeters. The table shows the diameters of steel pipes in millimeters, as well as in inches.

Nominal pipe diameter (Dy), mm	Thread diameter (G), inch	Pipe outer diameter (Dh), mm
		Pipe steel water and gas	seamless	Polymer
10	3/8"	17	16	16
15	1/2"	21,3	20	20
20	3/4"	26,8	26	25
25	1"	33,5	32	32
32	1 1/4"	42,3	42	40
40	1 1/2"	48	45	50
50	2"	60	57	63
65	2 1/2"	75,5	76	75
80	3"	88,5	89	90
90	3 1/2"	101,3	102	110
100	4"	114	108	125
125	5"	140	133	140
150	6"	165	169	160

Video: How to make a hydraulic calculation

The diameter of the pipes in inches and millimeters are very important indicators. Many have faced the challenge of replacing or installing piping and finding the right materials for the job.

It is difficult to understand the huge number of proposals on the construction market, therefore, before buying, you should study in detail what the volume of pipe rolling is and how it is used in practice.

You can immediately use the online calculator below for translation without familiarizing yourself with the theory.

Online calculator for converting inches to millimeters and vice versa

An example of how to enter data into a calculator

In writing the size in inches, you should separate the integer part of the number from the fractional (if any) with a space: for example, 10 1/4, or 20 4/8; otherwise you get 101/4 and 204/8. Fractional numbers in millimeters are entered through a dot, not a comma (25.4 and not 25.4).

Enter the data for the calculation in the following. in order: click the left mouse button in the window of the corresponding parameter to make the blinking cursor appear; enter your numbers. The fractional part of an inch is entered without a sign.

1 inch = 25.4 millimeters (mm). Currently, an inch, due to its clarity, is often used to measure the diameters of water and gas pipes and threads. Many parts are also sized in multiples of inches. In addition to whole inches, measurements are taken in fourths (1/4″), eighths (1/8″), sixteenths (1/16″), thirty-seconds (1/32″) of an inch, etc.

If you have any questions about using the online calculator, you can always ask a question in the comment form. We also strongly recommend that you read the instructions (located under the calculator).

How to convert inch values ​​​​to metric notation

The conversion of inches to metric pipe volumes is performed using special tables. Here is an example of such a table:

The first table of diameters ( its symbolic designation is Ø, further it will be denoted in the article) of pipes shows values ​​in millimeters, while inches are used in the second table ( international designation - inch or in, will be further indicated in the article). An inexperienced master may ask why? And what designations are considered correct?

The reason is that the metric system is used all over the world. This system is based on two indicators: conditional and nominal volume. These concepts are approached in different ways, but in the end they show the external volume. In essence, these quantities are dimensionless, but sometimes they are indicated in millimeters.

Analyzing tabular data, it is possible to compare products of domestic manufacturers and analogues of foreign production.

Interesting! Measurement discrepancies appeared simultaneously with the introduction of copper systems in Europe in the second half of the 20th century. In Russia at that time the standards for the metal assortment were determined in mm, and not in inch, this measurement system is widely used today.

Correspondence of two notation systems

Steel pipes are widely used in water and gas systems. Their dimensions are shown in whole values ​​or their fractions. For example, a 1" tubular in mm would be 33.5, and a 2" tubular would be 67 in mm.

This of course does not correspond to the declared 25.4 and 50 mm. When laying fittings with inch designations for 1 and 2 inch products, there are no difficulties, but replacing with plastic and copper products requires taking into account the discrepancy in the designations.

Why is everything so complicated? The fact is that for the formation of a fluid flow, it is important to take into account the internal size. For these reasons, they began to indicate exactly this indicator for 1-inch, 2-inch and all other pipe materials. The most accurate indicators are considered in terms of conditional passage.

The nominal bore of 1-inch, 2-inch and the rest of the pipe range is equal to the dimensions of the clearance. To indicate the metric size of 1 inch, 2 inch and any other pipeline, it is recommended to use tables.

Precise definitions - formula for calculation

This knowledge is needed to calculate the amount of transported medium. This is very important for heating systems. For example, when it is necessary to lay a heating system, it is necessary to determine and calculate the size of the assortment in the section so that all housing is heated evenly.

How to accurately determine the cross section of each pipe in quantities such as inches can be suggested by the formula: D \u003d sqrt ((314 ∙ Q) / (V ∙ DT)).

• D is the internal volume of the pipe;
• Q is the heat flux, which is determined in kW;
• V denotes the speed of the heat carrier, it is determined in m / s;
• DT is the difference in temperature indicators at the inlet and outlet of the network;
• sqrt is the square root.

Watch the video

Despite the presence of formulas, tables help to quickly determine Ø. In this way, a lot of time is saved.

What is inch volume

Deciphering the diameter of the pipes provided in inches is simple. They are often measured in these quantities. Such one unit is equal to 3.35 cm. It has already been indicated that the interpretation of this value has discrepancies, and this is due to the fact that the assortment is measured not by the external volume, but by the internal one. So, for example, the internal dimension of an inch pipe billet can be different: from 2.55 to 2.71 cm. This value varies depending on the wall thickness.

A 1 inch pipe has an outer diameter of 25.4 mm, a 2 inch pipe is 50 millimeters in metric measurement. Where do the numbers 33.249 and 66.498 come from in the technical parameters of a cylindrical pipe thread?

This thread on 1 and 2 inch products is performed on the outer volume. Therefore, the ratio of the thread diameter to the internal volume is conditional. Based on this, the dimensions of 1 and 2 inch tubing are calculated by adding the value of 25, 4 or 50 with two wall thicknesses of the tubular product.

Before deciphering, you need to take into account that measurements of the product must be performed not from the outside, but from the inside. Why is this needed? The fact is that by fastening sections of the highway from different materials, and taking measurements only from the outside, you can get the wrong result, which will lead to an error, since the entire assortment differs in wall dimensions.

Also, when deciphering, we must not forget that the standards of different manufacturers are different, they all focus on their own indicators.

If it is difficult to perform such decryption on your own, then you should seek help from professionals. They will provide effective assistance in choosing the right products.

Correspondence of metric and inch parameters

All tubular products are manufactured according to a certain standard, and the pressure indicator is a fixed value. Therefore, you need to know exactly the correspondence of the Ø of all pipes shown in inches and mm. Ignoring this correspondence, it is impossible to choose the right pipe assortment.

Watch the video

When selecting a certain size, they are guided by tabular information, and when replacing a guide, we serve as the most approximate parameter. There is no exact correspondence in two different systems of measurement, therefore pipeline elements are often equated in practice.

How this correspondence is applied in everyday life can be found in the table below:

Using this information, you can accurately determine the correspondence of two types of measurements of dimensions, and take parts for work that exactly match each other.

Inch size expression

These indicators are written as an integer, a double stroke is placed next to it, for example, 3 ". Also, the dimensions of the pipe diameter, transmitted in inches, are prescribed in fractions, for example, ½.

If we consider these dimensions on specific examples of Du correspondences, then they will look like this:

1. The diameter of a standard 12 inch pipe is 300.
2. 3 inch tubular diameter is 80.
3. 8 inch diameter of standard pipe is equal to 200.
4. The diameter of a standard pipe, at 32, when translated into inches, is shown as 1 ¼
5. Pipe diameter 40 mm in inch prescribe 1 ½
6. Ø standard pipe at 15 inches is expressed as a number ½
7. The Ø of a standard product per 4 inches in terms of metric is 100.
8. Ø 3/4 inch pipe in metric conversion is 20.
9. The Ø of a standard 1/2 inch pipe in metric translation shows the number 15.

Watch the video

Pipe diameter in inches and millimeters is used all the time. Knowing these dimensions, you can avoid great difficulties when connecting pipeline elements. And special tables help to find the necessary dimensions of the docking parts and correctly fit them.

Her Majesty Trumpet! It certainly makes our lives better. More or less like this:

The key characteristic of any cylindrical pipe is its diameter. It may be internal Do) and outer ( Dn). Pipe diameter is measured in millimeters, but the unit of pipe thread is inch.

At the junction of the metric and foreign systems of measurement, as a rule, the most questions arise.

In addition, the actual size of the inner diameter often does not match Dy.

Let's take a closer look at how we can live with this. A separate article is devoted to pipe threading. Read also about profile pipes, which are used for the construction of structures.

Inches versus mm. Where does the confusion come from and when is a correspondence table needed?

Pipes whose diameter is indicated in inches ( 1", 2" ) and/or fractions of an inch ( 1/2", 3/4" ), are the generally accepted standard in water and water and gas supply.

What is the difficulty?

Dimension the pipe diameter 1" (how to measure pipes is written below) and you will get 33.5mm, which naturally does not coincide with the classic linear table for converting inches to mm ( 25.4mm).

As a rule, installation of inch pipes takes place without difficulty, but when they are replaced with pipes made of plastic, copper and stainless steel, a problem arises - a mismatch in the size of the indicated inch ( 33.5mm) to its actual size ( 25.4mm).

Usually this fact is puzzling, but if you look deeper into the processes taking place in the pipe, then the logic of the size mismatch becomes obvious to the non-professional. It's pretty simple - read on.

The fact is that when creating a water flow, it is not the outer, but the inner diameter that plays a key role, and for this reason it is used to designate it.

However, the discrepancy between designated and metric inches still remains, because the internal diameter of a standard pipe is 27.1 mm, and enhanced - 25.5mm. The last value is pretty close to equality 1""=25,4 but still they are not.

The answer is that to designate the size of pipes, a nominal diameter rounded to a standard value is used (nominal bore Dy). The value of the conditional passage is selected so that the throughput of the pipeline increases from 40 to 60% depending on the growth of the index.

Example:

The outer diameter of the pipe system is equal to 159 mm, pipe wall thickness 7 mm. The exact inside diameter will be D \u003d 159 - 7 * 2 \u003d 145 mm. With wall thickness 5 mm size will be 149 mm. However, both in the first and in the second case, the conditional passage will have one nominal size 150 mm.

In situations with plastic pipes, transition elements are used to solve the problem of inappropriate sizes. If it is necessary to replace or join inch pipes with pipes made according to real metric dimensions - copper, stainless steel, aluminum, both the outer and inner diameters should be taken into account.

Nominal bore table in inches

Doo	inches	Doo	inches	Doo	inches
6	1/8"	150	6"	900	36"
8	1/4"	175	7"	1000	40"
10	3/8"	200	8"	1050	42"
15	1/2"	225	9"	1100	44"
20	3/4"	250	10"	1200	48"
25	1"	275	11"	1300	52"
32	1(1/4)"	300	12"	1400	56"
40	1(1/2)"	350	14"	1500	60"
50	2"	400	16"	1600	64"
65	2(1/2)"	450	18"	1700	68"
80	3"	500	20"	1800	72"
90	3(1/2)"	600	24"	1900	76"
100	4"	700	28"	2000	80"
125	5"	800	32"	2200	88"

Table. Inner and outer diameters. Stacked water / water and gas pipelines, electro-welded longitudinally welded, steel seamless hot-formed and polymer pipes

Correspondence table for the diameter of the nominal bore, thread and outer diameters of the pipeline in inches and mm.

Nominal pipe diameter Dy. mm	Thread diameter G". inch	Outer pipe diameter Dn. mm
		Stacked water/water/gas pipes GOST 3263-75	Pipes steel electrowelded longitudinal GOST 10704-91. Pipes steel seamless hot deformed GOST 8732-78. GOST 8731-74 (from 20 to 530 ml)	polymer pipe. PE, PP, PVC

GOST- state standard used in heat - gas - oil - pipelines

ISO- diameter designation standard, used in plumbing engineering systems

SMS- Swedish standard for pipe and valve diameters

DIN/EN- the main European assortment for steel pipes according to DIN2448 / DIN2458

DU (Dy)- conditional pass

Tables with the dimensions of polypropylene pipes are presented in the following article >>>

Correspondence table for the nominal diameter of pipes with international markings

GOST	ISO inch	ISO mm	SMS mm	DIN mm	DU
8	1/8	10,30			5
10	1/4	13,70	6,35		8
12	3/8	17,20	9,54	12,00	10
18	1/2	21,30	12,70	18,00	15
25	3/4	26,90	19,05	23(23)	20
32	1	33,70	25,00	28,00	25
38	1 ¼	42,40	31,75	34(35)	32
45	1½	48,30	38,00	40,43	40
57	2	60,30	50,80	52,53	50
76	2½	76,10	63,50	70,00	65
89	3	88,90	76,10	84,85	80
108	4	114,30	101,60	104,00	100
133	5	139,70	129,00	129,00	125
159	6	168,30	154,00	154,00	150
219	8	219,00	204,00	204,00	200
273	10	273,00	254,00	254,00	250

Diameters and other characteristics of stainless steel pipe

Pass, mm	Diameter outer, mm	Wall thickness, mm		Weight of 1 m pipe (kg)
		standard	reinforced	standard	reinforced
10	17	2.2	2.8	0.61	0.74
15	21.3	2.8	3.2	1.28	1.43
20	26.8	2.8	3.2	1.66	1.86
25	33.5	3.2	4	2.39	2.91
32	42.3	3.2	4	3.09	3.78
40	48	3.5	4	3.84	4.34
50	60	3.5	4.5	4.88	6.16
65	75.5	4	4.5	7.05	7.88
80	88.5	4	4.5	8.34	9.32
100	114	4.5	5	12.15	13.44
125	140	4.5	5.5	15.04	18.24
150	165	4.5	5.5	17.81	21.63

Did you know?

What ingenious lamps can be assembled with your own hands from an ordinary metal pipe? This is for everyone!

Which pipe is considered small - medium - large?

Even in serious sources, I had to observe phrases like: “We take any pipe of medium diameter and ...”, but no one indicates what this average diameter is.

To figure it out, you should first understand what diameter you need to focus on: it can be internal and external. The first is important when calculating the transport capacity of water or gas, and the second for determining the ability to withstand mechanical loads.

External diameters:

From 426 mm is considered large;

102-246 is called the average;

5-102 is classified as small.

As for the inner diameter, it is better to look at a special table (see above).

How to find out the pipe diameter? Measure!

For some reason, this strange question often comes to e-mail and I decided to supplement the material with a paragraph about metering.

In most cases, when buying, it is enough to look at the marking or ask the seller a question. But it happens that you need to repair one of the communication systems by replacing pipes, and initially it is not known what diameter the already installed ones have.

There are several ways to determine the diameter, but we will list only the simplest ones:

Arm yourself with a tape measure or measuring tape (women measure their waist like this). Wrap it around the pipe and record the measurement. Now, to obtain the desired characteristic, it is enough to divide the resulting figure by 3.1415 - this is the Pi number.

Example:

Imagine that in girth (circumference L) your pipe 59.2 mm. L=ΠD, resp. diameter will be: 59.2 / 3.1415= 18.85mm.

• After receiving the outer diameter, you can find out the inner one. Only for this you need to know the thickness of the walls (if there is a cut, just measure with a tape measure or other device with a millimeter scale).

  Assume that the wall thickness is 1 mm. This figure is multiplied by 2 (if the thickness is 3 mm, then it is also multiplied by 2 in any case) and subtracted from the outer diameter (18.85- (2 x 1 mm) = 16.85 mm).

  It's great if you have a caliper at home. The pipe is simply wrapped around the measuring teeth. We look at the desired value on a double scale.

Types of steel pipes according to their production method

Electrowelded (straight-seam)

For their manufacture, strips or sheet steel are used, which are bent to the desired diameter on special equipment, and then the ends are connected by welding.

The impact of electric welding guarantees a minimum joint width, which makes it possible to use them for the construction of gas pipelines or water pipelines. The metal in most cases is carbon or low-alloy.

The indicators of finished products are regulated by the following documents: GOST 10704-91, GOST 10705-80 GOST 10706-76.

At the same time, please note that a pipe made according to standard 10706-26 is distinguished by maximum strength among its own kind - after creating the first connecting seam, it is strengthened with four additional ones (2 inside and 2 outside).

The regulatory documentation indicates the diameters of products manufactured by electric welding. Their size is from 10 to 1420 mm.

Spiral-seam

The material for production is steel in rolls. Products are also characterized by the presence of a seam, but unlike the previous production method, it is wider, which means that the ability to withstand high internal pressure is lower. Therefore, they are not used for the construction of gas pipeline systems.

A specific type of pipe is regulated by GOST under the number 8696-74 .

Seamless

The production of a particular type involves the deformation of specially prepared steel blanks. The deformation process can be performed both under the influence of high temperatures and in a cold way (GOST 8732-78, 8731-74 and GOST 8734-75, respectively).

The absence of a seam has a positive effect on the strength characteristics - the internal pressure is evenly distributed over the walls (there are no "weak" places).

As for the diameters, the standards control their manufacture with a value of up to 250 mm. When buying products with sizes exceeding those indicated, you have to rely only on the integrity of the manufacturer.

It's important to know!

If you want to buy the most durable material, buy cold-formed seamless pipes. The absence of temperature effects has a positive effect on the preservation of the original characteristics of the metal.

Also, if an important indicator is the ability to withstand internal pressure, then choose round products. Profile pipes cope better with mechanical loads (metal frames are well made from them, etc.).

Here are a couple more great slides of creative advertising for a pipe manufacturer: