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How to determine the size of the pipe in inches: 15 curious facts

In this article I am going to talk about how the sizes of pipes in inches and millimeters relate. In addition, we with the reader will have a little excursion to the history of length measures and in the current regulatory documentation. So, on the road.

History in

1. The origin of the word "inches" is derived from Dutch DUIM, which literally means "thumb". However, as an international designation of this measure, another word is used - inch;
2. Like all the old measures of length, inch originates in human anthropometry and equal to the length of the phalanx at your thumb. In addition, it is equal to 1/12 feet (from the English foot - foot foot) and 1/36 yard (according to legends, the yard was equal to the distance from the nose to the end of the thumb out of the hands of the King of Britain Heinrich first);

There is an opinion that the Sword of Heinrich had a length of one yard.

1. In different countries and at different times, the inch took different meanings. Viennese inches (Austro-Hungary) is 2.63 cm, French - 2,707, Starolar - 2.48, Novopolsky - 2.4, Prussian sample of 1816 - and at all 3.766 cm;
2. In Russia, this measure of length was introduced by Peter first. Prior to that, in trade and during the calculations, domestic units of measurement were used, also based on anthropometry - tops (the length of the first phalange of the index finger), the span (it is measured between the largest and index fingers diluted at the maximum distance (the length of the adult step);
3. Currently, the most common is the English inch. Since 1958, it agreed to consider it equal to 2.54 cm.

About Bardaka

Dear reader, do you think that it is possible to calculate the cross section of the steel pipe or the cigrier in inches, using the caliper and dividing the resulting result by 25.4? Not there was something.

Conditional pass

1. Steel water-gas pipes, whose cross section is taken in inches, are marked at all with a diameter, but by conditional passage. It is close to the inner section, but not necessarily equal to him. It only means that on the nozzle, you can cut the corresponding pipe thread;

1. The actual inner diameter is determined by the conditional passage (more precisely, corresponding to it by the outer diameter) and the type of pipe (it may be ordinary, light or reinforced);
2. The actual internal cross section of products with the same Du (conditional passage) may vary by 0.3 cm due to the walls;
3. The area of \u200b\u200bthe internal section and, accordingly, the throughput capacity of a light and enhanced pipe with a nominal size of half theft differ by 20%. At the same time, the capacity of the light product, but in reinforced due to the greater the thickness of the walls and, accordingly, the greater mass of the route is higher than the price.

Pipe rolling samples produced according to GOST 3262 - 75.

Standards

With all my immeasurable respect for the Soviet standardization system, otherwise, as a mess, how according to current standards, the sizes of pipes in inches and centimeters are correlated:

1. Specified in the documentation section in inches cannot be obtained by a simple recalculation of mm or other units C. a conversion factor for each diameter and in any case do not corresponds quite logical value of 25.4;
2. To determine the number of inches on the measurement results, you will have to climb into reference or regulatory documentation. but none in the GOST does not appear the table sizes in inches and millimeters. Actual dimensions with a certain DU and the type of product can be found in GOST 3262-75, which regulates the production of steel black and galvanized water-gas pipes. Meanwhile, the parameters of the corresponding threads are indicated in the other GOST - for the number 6357-81.

The second standard indicates the dimensions of the ridges and the threads in units of C, but denotes the cylindrical tube thread in inches.

Easier, even easier

So, to relate the size of the pipe in inches and mm, you need to be laid out with regulatory documents and painstakingly compare them. So?

Dear reader, I will not tomatize you and simply post a pair of tables, which are compilation of the standards mentioned above.

1. Here is the correspondence of the Du and cherished British inches:

control	Inches
15	1/2
20	3/4
25	1
32	1 1/4
40	1 1/2
50	2
65	2 1/2
80	3
90	3 1/2
100	4
125	5
150	6

In addition to these, GOST 3262-75 provides conditional passages 6, 8 and 10. However, they do not apply in the plumbing, and do not find threaded fittings.

The minimum cross section used in the plumbing is DU 15.

1. But the ratio of Du and actual dimensions:

control	External diameter	Wall thickness
		Stregnated	Ordinary	Easy
15	21,3	3,2	2,8	2,5
20	26,8	3,2	2,8	2,5
25	33,5	4	3,2	2,8
32	42,3	4	3,2	2,8
40	48	4	3,5	3
50	60	4,5	3,5	3
65	75,5	4,5	4	3,2
80	88,5	4,5	4	3,5
90	101,3	4,5	4	3,5
100	114	5,0	4,5	4
125	140	5,5	4,5	4
150	165	5,5	4,5	4

How, using these tables, you can calculate the actual dimensions of the pipe 1 inch? Very simple:

In our case, one inch corresponds to the conditional passage of DU 25 and means the outer diameter of 33.5 mm. The inner diameter of the lung tube will be equal to 28.1 mm, ordinary - 27.1, and reinforced - 25.5 mm.

Polymer and metal-polymer pipes

1. They are always marked by an outer diameter of millimeters; The wall thickness is indicated either in marking, or in technical documentation. To get the same as the steel eyeliner of a known size, bandwidth, you need to choose a product with the same inner diameter. Let me remind you, it is calculated as a difference between the diameter and the double wall thickness;

To collect any communication system without fulfilling the compounds will not work at least, because, in the end, it will be needed to connect plumbing equipment. The main thing is to get a quality assembly, and the diameters of all connections accurately matched. Below we will tell a little about the inch tube.

Difference of pipes for dimensional parameters

Whether it is pipes from plastic, metal or ceramics, they have a list of characteristics by which the buyer is focused when choosing them.

The main indicators include the following:

• external section - if the pipe is round;
• internal section - is considered to be a working diameter;
• wall thickness - characterizes, as a rule, the strength of the pipe.

The outer cross section is formed from the inner section and the wall thickness multiplied by two. Often pipes are connected by a threaded way. The thread is applied to the exterior of the pipe, after which its diameter can not be considered equal to the outer diameter of the pipe. And due to the fact that when mounting, it is necessary to repel from the thread cross section, this value is becoming more important, and, as a rule, is taken into account instead of the actual size of the pipe.

For example, inch pipes in MM will not be equal to 25.4, because in this case 1 inches indicates the thread section. Everything is complicated due to the existence of two measurement systems, and in view of the presence in the market a plurality of similar products.

Conditional pipe bandwidth

Such a parameter is called conditional passage and denotes DN characters. There is no specific unit of measure, therefore only a conditional, non-infact parameter, which in integer expression determines the approximate lumen of the pipe. The gaps between the values \u200b\u200bare calculated theoretically, so that, upon subsequent value, the bandwidth of pipes increased by 40-60%.

The efficiency of the finished system will be visible only in practice. To obtain a properly functioning system of the water supply system, you just need to use the table in which the list of water pipes with the corresponding fittings are specified to comply with conditional passages.

It is easy to conclude that in an inch tube the diameter of the inside will be 25.5 mm, the outer cross section will be 33.25 mm.

Methods for measuring pipe cross section

There are two pipe measurement systems:

• Imperial. The calculus unit is inches. It is used to designate only water and gas pipeline pipes and concomitant water reinforcement.
• Metric. Calculated in millimeters, centimeters and meters. Used for pipes used for other purposes.

Differences between metric and inch pipes

You can find both steel inch and standard pipes, which can also cause confusion. Unite they differ in the form of a thread - the thread inch pipe is rounded.

Thread step can be measured in various ways. In the inch pipes, measurements are made on the internal boundaries of the threads, and in metric pipes - by external.

Different pipe diameters will be different distances:

• for half a pipe and pipes three quarters, a step will be 1.81 mm;
• 1-6 inches - 2.31 mm.

Conversion of sections inch to metric

Relevant tables can be found in reference books. In the same GUT, defining the parameters of the WGP, there are indicators of conditional bandwidths in millimeters and in inches. However, to create a functioning system, indicators of the actual internal cross section are needed. At the same time, in tables, as a rule, you can find only outdoor sections.

Ideally, the tables in inches, the external section of the pipe and the corresponding section in millimeters will be included in the table.

For example, a steel one inch tube can be connected to a plastic, the conditional bandwidth of which is 25 mm.

Usually, in the notation of the diameters of pipes, values \u200b\u200bare used in inches, so we suggest you get acquainted with the table, where the values \u200b\u200bin inches are translated into millimeters. In scientific literature, use the concept of "conditional passage".

Under "Conditional Passage" realize size (diameter conditional), conventionally characterizing inner diameter and is not necessarily coincident with the actual inside diameter. Conditional passage is taken from a standard row

1Dype \u003d 25.4 mm

Please note that if we take a pipe for 1 "(one inch), then the outer diameter is not equal to 25.4 mm. Here it begins the confusion -"Pipe inches". Let's try to clarify this question. If you look at the parameters of pipe cylindrical thread, then notice that the outer diameter (at one inches) is 33.249 mm, and not 25.4.

The nominal diameter of the thread is conditionally attributed to the inner diameter of the pipe, and the thread is cut on the outer diameter. Here we get the diameter - 25.4 mm + two thicknesses of the pipe wall ≈ 33.249 mm. Thus appeared"Pipe inch".

Diameters in inches	Adopted conditional diameters of pipes, mm	The external dimensions of the steel pipe according to GOST 3262-75, mm
½ "	15	21,3
¾ "	20	26,8
1 "	25	33,5
1 ¼ "	32	42,3
1 ½ "	40	48
2 "	50	60
2 ½"	65	75,5
3 ""	80	88,5
4 "	100	114

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inches	mm.	inches	mm.	inches	mm.	inches	mm.	inches	mm.
-	-	1	25,4	2	50,8	3	76,2	4	101,6
1/8	3,2	1 1/8	28,6	2 1/8	54,0	3 1/8	79,4	4 1/8	104,8
1/4	6,4	1 1/4	31,8	2 1/4	57,2	3 1/4	82,6	4 1/4	108,8
3/8	9,5	1 3/8	34,9	2 3/8	60,3	3 3/8	85,7	4 3/8	111,1
1/2	12,7	1 1/2	38,1	2 1/2	63,5	3 1/2	88,9	4 1/2	114,3
5/8	15,9	1 5/8	41,3	2 5/8	66,7	3 5/8	92,1	4 5/8	117,5
3/4	19,0	1 3/4	44,4	2 3/4	69,8	3 3/4	95,2	4 3/4	120,6
7/8	22,2	1 7/8	47,6	2 7/8	73,0	3 7/8	98,4	4 7/8	123,8

Parameters of inch threads

The outer diameter of the pipe connected		SAE thread rating	Nominal Threads UNF.	The outer thread diameter, mm	The average diameter of the thread, mm	Pitch thread
mM.	inch					mM.	thread / inch
6	1/4""""	1/4""""	7/16""""-20	11,079	9,738	1,27	20
8	5/16""""	5/16""""	5/8""""-18	15,839	14,348	1,411	18
10	3/8""""	3/8""""	5/8""""-18	15,839	14,348	1,411	18
12	1/2""""	1/2""""	3/4""""-16	19,012	17,33	1,588	16
16	5/8""""	5/8""""	7/8""""-14	22,184	20,262	1,814	14
18	3/4""""	3/4""""	1""""-14	25,357	23,437	1,814	14
18	3/4""""	---	1""""1/16-14	26,947	25,024	1,814	14
20	7/8""""	---	1""""1/8-12	28,529	26,284	2,117	12
22	7/8""""	7/8""""	1""""1/4-12	31,704	29,459	2,117	12
22	7/8""""	---	1""""3/8-12	34,877	32,634	2,117	12
25	1""""	1""""	1""""1/2-12	38,052	35,809	2,117	12

Copper veins, wires and cables

Section of conductive veins, mm	Copper veins, wires and cables
	Voltage, 220 V		Voltage, 380 V
	Talk, A.	power, kWt	Talk, A.	power, kWt
1,5	19	4,1	16	10,5
2,5	27	5,9	25	16,5
4	38	8,3	30	19,8
6	46	10,1	40	26,4
10	70	15,4	50	33,0
16	85	18,7	75	49,5
25	115	25,3	90	59,4
35	135	29,7	115	75,9
50	175	38,5	145	95,7
70	215	47,3	180	118,8
95	260	57,2	220	145,2
120	300	66,0	260	171,6

Aluminum conductors, wires and cables

The cross section of the current veins, mm	Aluminum veins, wires and cables
	Voltage, 220 V		Voltage, 380 V
	Talk, A.	power, kWt	Talk, A.	power, kWt
2,5	20	4,4	19	12,5
4	28	6,1	29	15,1
6	36	7,9	30	19,8
10	50	11,0	39	25,7
16	60	13,2	55	36,3
25	85	18,7	70	46,2
35	100	22,0	85	56,1
50	135	29,7	110	72,6
70	165	36,3	140	92,4
95	200	44,0	170	112,2
120	230	50,6	200	132,0

Dimensions of inch thread

	Thread diameter in mm			Thread step in mm	Number of threads per 1 "
	external d	Middle D.	Inner D.
3/16	4,762	4,085	3,408	1,058	24
1/4	6,350	5,537	4,724	1,270	20
5/16	7,938	7,034	6,131	1,411	18
3/8	9,525	8,509	7,492	1,588	16
1/2	12,700	11,345	9,989	2,117	12
5,8	15,875	14,397	12,918	2,309	11
3/4	19,05	17,424	15,798	2,540	10
7/8	22,225	20,418	18,611	2,822	9
1	25,400	23,367	21,334	3,175	8
1 1/8	28,575	26,252	23,929	3,629	7
1 1/4	31,750	29,427	27,104	3,629	7
1 1/2	38,100	35,39	32,679	4,233	6
1 3/4	44,450	41,198	37,945	5,080	5
2	50,800	47,186	43,572	5,644	4 1/2

Nominal thread diameter in inches
	Thread diameter in mm			Thread step in mm	Number of threads per 1 "
	external d	Middle D.	Inner D.
1/8	9,729	9,148	8,567	0,907	28
1/4	13,158	12,302	11,446	1,337	19
3/8	16,663	15,807	14,951	1,337	19
1/2	20,956	19,794	18,632	1,814	14
5/8	22,912	21,750	20,588	1,814	14
3/4	26,442	25,281	24,119	1,814	14
7/8	30,202	29,040	27,878	1,814	14
1	33,250	31,771	30.293	2,309	11
1 1/8	37,898	36,420	34,941	2,309	11
1 1/4	41,912	40,433	38,954	2,309	11
1 3/8	44,325	32,846	41,367	2,309	11
1 1/2	47,805	46,326	44,847	2,309	11
1 3/4	53,748	52,270	50,791	2,309	11
2	59,616	58,137	56,659	2,309	11

Table of translation units

Translation of energy units	Translation of pressure units
1 J \u003d 0.24 Cal	1 Pa \u003d 1 n / m * m
1 kJ \u003d 0.28 W * h	1 Pa \u003d 0.102 kg / m * m
1 W \u003d 1 J / s	1 atm \u003d 0,101 MPa \u003d 1.013 bar
1 Cal \u003d 4.2 J	1 bar \u003d 100 kPa \u003d 0,987 atm
1 kcal / h \u003d 1,163 W	1 psi \u003d 0,06895 bar \u003d 0,06805 atm

Translation table of inch sizes in metric. Thread Size: Table of metric and inch threads

The process of selecting the required cross-section thread sizes of cables and pipes often causes a lot of time. In addition to choosing suitable dimensions, taking into account the equipment parameters, the customer has to independently translate data into suitable units of measurement. Such a process is turning to be significant temporary costs.

We simplify this task, as we suggest you to use the ready-made translation tables. On the page of our site you will find tables that will help you easily choose the necessary threads of inch pipes, copper and aluminum wires and cables. Also, you can use the table of translation in the metric, thereby accurately calculate the necessary section sizes.

Unfortunately, most equipment manufacturers leave the customer one to one with the execution of calculations. Therefore, a person has to independently search for a translation table on the Internet to select the optimal size of the cross-section of the wires and diameters of pipes.

We value the time of our customers, providing everyone to the use of ready-made solutions. In our tables, standard dimensions of inches per millimeters are translated.

On this page, you will also find the translations of the main energy units and pressure units, therefore, be able to correctly select refrigeration equipment, given the individual conditions of placement and operating modes of aggregates.

The geometric sizes of pipes are determined by the following characteristics:

• - external diameter;
• - wall thickness;
• - the ratio of external and internal diameters;
• - Length.

Sort of pipes (Available sizes, technical conditions for the production and use of steel pipes) are normalized by government standards by GOST). GOSTS are developed taking into account the technology of manufacturing pipes and used in the production of steels.

In the CIS market, it is customary to indicate the sizes of pipes in mm (millimeters), but you can also meet the sizes of pipes in inches. The latter are most often indicated for imported pipes. Pipe rental length is measured in meters.

Diameter of steel pipes

The diameter of the steel pipe is determined by:

• - external diameter for electric welded and seamless pipes;
• - diameter of the conditional passage for VGP pipes.

• — Diameter of conditional passage (Du or DU) - internal pipe diameter.
• — Conditional pass - The conditional value, which is the value of the actual internal diaphretis, rounded to the nearest of the standard row, and serves as a reference point for selecting the size of the other parts and equipment. Its value standardized according to GOST 28338-89. Measured in inches or mm.
• — Inner diameter - the actual value of the parameter obtained by direct measurement is typically indicated in mm;
• — Outer diameter of pipes (DN or DN) - the actual diameter of the pipe, taking into account the wall thickness, is indicated in mm;
• — Diameter of thread(G).

The sizes of the pipes are indicated in millions, but for the PCP tube are often denoted in inches (").

Table matching pipe diameters in mm and inches

Conditional Pipe Pipe (DY), mm	Thread diameter (G), inch	Outer diameter of the pipe (DN), mm
		Water pipe steel pipe	Steel pipe seamless	Polymer

Dimensions VGP-pipes according to GOST 3262-75

The main dimensions of the VGP pipe: 15 mm (1/2 "inches); 20 mm (3/4"); 25 mm (1 "); 32 mm (1 1/4" inch with a quarter); 40 mm (1 1/2 "); 50 mm (2"). There are also the following DU: 10 mm, 65 mm, 80 mm, 90 mm, 100 mm, and even 125 mm - but they are rarely used and, as a rule, are replaced by other types of steel pipes (for example, electric welded). Most often for risers are used pipes 3/4 "for internal wiring 1/2".

Sizes of electric weld pipes according to GOST 10704-91

Statery electric weld pipes are the following outer diameters (in millimeters): 10; 12; 13; fourteen; sixteen; 17; 17.5; eighteen; nineteen; twenty; 21.3; 22; 24; 25; 26; 28; thirty; 32; 33; 33.7; 36; 38; 40; 42; 43; 45; 48; 51. With a diameter of up to 57 mm, the VGP tube of the appropriate size is used. The most popular dialing pipes according to GOST 10704-91 in size from 57 mm and above. Their main diameters: 57; 60; 63.5; 76; 89; 102; 108; 114; 127; 133; 140; 146; 159; 168; 178; 193; 219; 245; 273; 325; 377; 426; 530.

Sizes of welded pipes for gas and oil pipelines according to GOST 20295-85

Start with a diameter of 159 mm and up to 530 mm go with the same dimensions as the pipes according to GOST 10704-91. Basic larger diameters (in millimeters): 630, 720, 820, 1020,1220, 1420.

The size of hot-rolled seamless pipes according to GOST 8732-78

Frequently used diameters of seamless hot-focused pipes (mm): 32; 38; 42; 45; 51; 54; 57; 60; 63.5; 68; 70; 73; 76; 83; 89; 95; 102; 108; 114; 121; 127; 133; 140; 146; 152; 159; 168; 180; 194; 203; 219; 245; 273; 325; 351; 426.

Plants Manufacturers can make any pipe sizes at the request of the customer.

Internal diameters of pipes

According to the standard row adopted in most countries pipe They have the following inner diameter measured in mm: 6, 10, 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, 200, etc.

When installing the system of steel pipes for residential buildings, pipes are usually used with the size of the internal diameter DU \u003d 15, 20 and 32 mm.

External pipe diameters and pipe wall thickness

Outer diameter, DN mm	Wall thickness, mm
Steel water pipes GOST 3262-75
steel tubes GOST 10704-91 and GOST 10705-80

Conditional pass	Outside diameter	Pipe wall thickness
		lungs	ordinary	reinforced
6	10,2	1,8	2,0	2,5
8	13,5	2,0	2,2	2,8
10	17,0	2,0	2,2	2,8
15	21,3	2,35	—	—
15	21,3	2,5	2,8	3,2
20	26,8	2,35	—	—
20	26,8	2,5	2,8	3,2
25	33,5	2,8	3,2	4,0
32	42,3	2,8	3,2	4,0
40	48,0	3,0	3,5	4,0
50	60,0	3,0	3,5	4,5
65	75,5	3,2	4,0	4,5
80	88,5	3,5	4,0	4,5
90	101,3	3,5	4,0	4,5
100	114,0	4,0	4,5	5,0
125	140,0	4,0	4,5	5,5
150	165,0	4,0	4,5	5,5