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Pipe Size Chart | NPS, DN, NB, Outside / Inside Diameter, Wall Thickness

Before the invention of pipes, people used to carry water from lakes, ponds and reservoirs to their homes and fields. As this was a time consuming and tedious job, the idea of pipe was born using bamboos. But since the mid 1800’s, steel pipe became popular in the U.S. to carry water. Pipes are used in residential, commercial, industrial and agricultural applications to carry water, fuel, gases and other fluids. As different sizes of pipes are needed for different types of jobs, it is essential to grasp how the pipe sizes work with the help of a Pipe Size Chart.

So, in this article, we will learn about different types of pipes, the nomenclature associated with pipe size and also a pipe size chart for commonly used pipe sizes.

Pipes and Types of Pipes

In a general sense, a pipe is nothing but a hollow and tubular structure that is used to carry liquids, gases and fluids in general. Depending on the application, cost and other factors, pipes are made from a variety of materials. Some of the popular piping materials are:

  • Copper
  • Aluminum
  • Cast Iron
  • Plastic
  • Lead
  • Glass
  • Brass
  • Steel
  • Steel Alloys

1. Steel Pipe

It is one of the popular types of pipes used in high pressure and temperature situations to transport water, oil, gas and steam. In fact, since 1850s, steel pipes are used in the U.S. to carry water. Depending on their cross-sectional configuration, steel pipes are usually classified into Standard, Extra Strong and Double Extra Strong.

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2. Plastic Pipe

Modern day’s piping consists of mostly Plastic Pipes as they are cheaper to manufacture, easy to install and have higher resistance to corrosion. They are used to carry water, gas and oil but rarely used where temperature and pressure plays a major factor.

3. Cast Iron Pipe

Another popular pipe type is the Cast Iron Pipe. It is generally used to carry water, gas and drainage in the underground. Low-pressure steam can also be transported using cast iron pipes.

4. Copper Pipes

If corrosion is a main concern, then Brass or Copper Pipes can be used as an alternative to steel or cast-iron pipes. They have significantly better resistance to corrosion and can last longer when used in a corrosion prone environment. Copper pipes are also used in industrial application involving hydraulic and pneumatic systems.

Pipe Sizing

With the advancement in manufacturing process of pipes, we are able to produce pipes with specific characteristics such as its strength, temperature and pressure ratings, corrosion resistance, thickness and size. As there are multiple ways to categorize pipes, be it its manufacturing process, its final form or other characteristics, categorizing pipes based on size is a simple and basic method.

Different institutes and organizations have put a lot of effort into standardizing pipe sizes. One such organization is the American National Standards Institute (ANSI), which standardized pipe sizes, color code, nameplates and legends.

Typically, a pipe has four characteristics to be categorized based on size. They are:

  • Nominal Pipe Size
  • Outer Diameter
  • Inner Diameter
  • Wall Thickness

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From the above image, you can easily understand the different dimensions of a pipe.

What is Nominal Pipe Size, Nominal Bore and Nominal Diameter in Pipe Sizes?

Nominal Pipe Size or NPS is an easy way to identify pipes based on a vague representation of the outer diameter of the pipe. It is used in the Unites States and it is just a “nominal” size of the pipe without any dimensions.

For example, an NPS 6 doesn’t exactly have its outer diameter of 6inches. It is actually 6.625inches. Another important point to note about NPS representation is for NPS 1/8 to NPS12, the diameter is measured from the center of the wall. Hence, the outer diameter will be slightly higher than the NPS value.

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But from NPS14 onwards, the outer diameter and the NPS values are the same. So, NPS14 corresponds to a pipe with 14inch outer diameter.

While NPS is predominantly used in the U.S., the term Nominal Bore or NB is NPS equivalent in Europe (and other parts of the World). Except for the difference in names, both NPS and NB are the same.

Nominal Diameter (sometimes Diameter Nominal) or DN is the metric representation of the pipe size and hence the units are in millimeter. It is used everywhere in the World except North America. DN measures the inner diameter of the pipe and is roughly equal to 25 times the NPS.

Pipe Wall Thickness and Scheduling

The pipe wall thickness is an important dimension associated with pipes. Like NPS, even the wall thickness is denoted using a simple naming system called Schedule (SCH). Higher the wall thickness or schedule, greater is the strength of the pipe.

Originally, pipe wall thickness is categorized into three types:

  • Standard (Std)
  • Extra Strong (XS)
  • Double Extra Strong (XXS)

The usage of pipes in industries and different pressure and temperature environments lead to new pipe wall thickness nomenclature.

  • SCH5
  • SCH10
  • SCH10S
  • SCH20
  • SCH30
  • SCH40
  • SCH40S
  • SCH60
  • SCH80
  • SCH80S
  • SCH100
  • SCH120
  • SCH140
  • SCH160
NOTE: The ‘S’ in the above schedule naming system means it is a stainless-steel pipe.

In the new schedule naming system, the following can be observed:

  • For NPS1/8 to NPS10, Standard (Std) Schedule is similar to SCH40 and SCH40S.
  • For NPS1/8 to NPS8, Extra Strong (XS) Schedule is similar to SCH80 and SCH80S.
  • Foe NPS1/8 to NPS6, Double Extra Strong (XXS) Schedule is similar to SCH160.
  • For NPS8 and larger size pipes, SCH160 is thicker than XXS.

Pipe Size Chart

If you are new to pipes and its terminology, then Pipe Sizes can be confusing. Earlier, the pipe size was based on the inner diameter of the pipe. But this system had problems when using pipe fittings for the outer diameter.

Now-a-days, Pipe Sizes generally consists of Outer (or Outside) Diameter (sometimes NPS) and Wall Thickness. Let us now see some pipe size charts for commonly used pipe sizes.

In the first Pipe Size Chart, we will list out all the common pipe sizes until (and including) NPS12 as this is the limit where NPS and Outer Diameter are different. In the second pipe size chart, we will list out all the common pipe sizes starting from NPS14.

Pipe Size Chart for NPS1/8 to NPS12

For the sake of simple visual representation, we will further split the table into multiple sections as there are too many rows to fill.

Nominal Pipe Size (NPS) Diameter Nominal (DN) Outer Diameter Wall Identification Inner Diameter Wall Thickness
in mm in mm Iron Pipe Size Steel Schedule Number Stainless Steel Schedule Number in mm in mm
1/8 3 0.405 10.29 10S 0.307 7.8 0.049 1.24
Std 40 40S 0.269 6.83 0.068 1.73
XS 80 80S 0.215 5.46 0.095 2.41
1/4 6 0.504 13.72 10S 0.41 10.41 0.065 1.65
Std 40 40S 0.364 9.25 0.088 2.24
XS 80 80S 0.302 7.67 0.119 3.02
3/8 10 0.675 17.15 10S 0.545 13.84 0.065 1.65
Std 40 40S 0.493 12.52 0.091 2.31
XS 80 80S 0.423 10.74 0.126 3.2
1/2 15 0.84 21.34 5S 0.71 18.03 0.065 1.65
10S 0.674 17.12 0.083 2.11
Std 40 40S 0.622 15.8 0.109 2.77
XS 80 80S 0.546 13.87 0.147 3.73
160 0.466 11.84 0.187 4.75
XXS 0.252 6.4 0.294 7.47
3/4 20 1.05 26.67 5S 0.92 23.37 0.065 1.65
10S 0.884 22.45 0.083 2.11
Std 40 40S 0.824 20.93 0.133 2.87
XS 80 80S 0.742 18.85 0.154 3.91
160 0.612 15.54 0.219 5.56
XXS 0.434 11.02 0.308 7.82
1 25 1.315 33.4 5S 1.185 30.1 0.065 1.65
10S 1.097 27.86 0.109 2.77
Std 40 40S 1.049 26.64 0.133 3.38
XS 80 80S 0.957 24.31 0.179 4.55
160 0.815 20.7 0.25 6.35
XXS 0.599 15.21 0.358 9.09
1-1/4 32 1.66 42.16 5S 1.53 38.86 0.065 1.65
10S 1.442 36.63 0.109 2.77
Std 40 40S 1.38 35.05 0.14 3.56
XS 80 80S 1.278 32.46 0.191 4.85
160 1.16 29.46 0.25 6.35
XXS 0.896 22.76 0.382 9.7
1-1/2 40 1.9 48.26 5S 1.77 44.96 0.065 1.65
10S 1.682 42.72 0.109 2.77
Std 40 40S 1.61 40.89 0.145 3.68
XS 80 80S 1.5 38.1 0.2 5.08
160 1.338 33.99 0.281 7.14
XXS 1.1 27.94 0.4 10.16
2 50 2.375 60.32 5S 2.245 57.02 0.065 1.65
10S 2.157 54.79 0.109 2.77
Std 40 40S 2.067 52.5 0.154 3.91
XS 80 80S 1.939 49.25 0.218 5.54
160 1.687 42.85 0.344 8.34
XXS 1.503 38.18 0.436 11.07
2-1/2 65 2.875 73.02 5S 2.709 68.81 0.083 2.11
10S 2.635 66.93 0.12 3.05
Std 40 40S 2.469 62.71 0.203 5.16
XS 80 80S 2.323 59 0.276 7.01
160 2.125 53.97 0.375 9.52
XXS 1.771 44.98 0.552 14.02
3 80 3.5 88.9 5S 3.334 84.68 0.083 2.11
10S 3.26 82.8 0.12 3.05
Std 40 40S 3.086 77.93 0.216 5.49
XS 80 80S 2.9 73.66 0.3 7.62
160 2.624 66.65 0.438 11.13
XXS 2.3 58.42 0.6 15.24
3-1/2 90 4 101.6 5S 3.834 97.38 0.083 2.11
10S 3.76 95.5 0.12 3.05
Std 40 40S 3.548 90.12 0.226 5.74
XS 80 80S 3.364 85.45 0.318 8.08
4 100 4.5 114.3 5S 4.334 108.08 0.083 2.11
10S 4.26 108.2 0.12 3.05
Std 40 40S 4.026 102.26 0.237 6.02
XS 80 80S 3.826 97.18 0.337 8.56
120 3.624 92.05 0.438 11.12
160 3.438 87.33 0.531 13.49
XXS 3.152 80.06 0.674 17.12
5 125 5.563 141.3 5S 5.345 135.76 0.109 2.77
10S 5.295 134.49 0.134 3.4
Std 40 40S 5.047 128.19 0.258 6.55
XS 80 80S 4.813 122.25 0.375 9.52
120 4.563 115.9 0.5 12.7
160 4.313 109.55 0.625 15.88
XXS 4.063 103.2 0.75 19.05
6 150 6.625 168.27 5S 6.407 162.74 0.109 2.77
10S 6.357 161.47 0.134 3.4
Std 40 40S 6.065 154.05 0.28 7.11
XS 80 80S 5.761 146.33 0.432 10.97
120 5.501 139.73 0.562 14.27
160 5.187 131.75 0.719 18.26
XXS 4.897 124.38 0.864 21.95
8 200 8.625 219.08 5S 8.407 213.54 0.109 2.77
10S 8.329 211.56 0.148 3.76
20 8.125 206.38 0.25 6.35
30 8.071 205 0.277 7.04
Std 40 40S 7.891 202.72 0.322 8.18
60 7.813 198.45 0.406 10.31
XS 80 80S 7.625 193.67 0.5 12.7
100 7.437 188.9 0.594 15.09
120 7.187 182.55 0.719 18.26
140 7.001 177.83 0.812 20.62
XXS 6.875 174.63 0.975 22.22
160 6.813 173.05 0.906 23.01
10 250 10.75 273.05 5S 10.482 266.24 0.134 3.4
10S 10.42 264.67 0.165 4.19
20 10.25 260.35 0.25 6.35
30 10.136 257.45 0.307 7.8
Std 40 40S 10.02 254.51 0.365 9.27
XS 60 80S 9.75 247.65 0.5 12.7
80 9.562 242.87 0.594 15.09
100 9.312 236.52 0.719 18.26
120 9.062 230.17 0.844 21.44
XXS 140 8.75 222.25 1 25.4
160 8.5 215.9 1.125 28.57
12 300 12.75 323.9 5S 12.438 315.93 0.156 3.96
10S 12.39 314.71 0.18 4.57
20 12.25 311.15 0.25 6.35
30 12.09 307.09 0.33 8.38
Std 40S 12 304.8 0.375 9.52
40 11.938 303.23 0.406 10.31
XS 80S 11.75 298.45 0.5 12.7
60 11.626 295.3 0.562 14.27
80 11.374 288.9 0.688 17.47
100 11.062 280.97 0.844 21.44
XXS 120 10.75 273.05 1 25.4
140 10.5 266.7 1.125 28.57
160 10.126 257.2 1.312 33.32

Pipe Size Chart for NPS14 and above

For the sake of simple visual representation, we will further split the table into multiple sections as there are too many rows to fill.

Nominal Pipe Size (NPS) Diameter Nominal (DN) Outer Diameter Wall Identification Inner Diameter Wall Thickness
in mm in mm Iron Pipe Size Steel Schedule Number Stainless Steel Schedule Number in mm in mm
14 350 14 355.6 5S 13.688 347.68 0.156 3.96
10S 13.624 346.05 0.188 4.77
10 13.5 342.9 0.25 6.35
20 13.376 339.75 0.312 7.92
Std 30 13.250 336.55 0.375 9.52
40 13.124 333.35 0.438 11.13
XS 13 330.20 0.5 12.7
60 12.812 325.42 0.594 15.09
80 12.5 317.5 0.75 19.05
100 12.124 307.95 0.938 23.82
120 11.812 300.02 1.094 27.79
140 11.5 292.1 1.25 31.75
160 11.188 284.18 1.406 35.71
16 400 16 406.4 5S 15.67 398.02 0.165 4.19
10S 15.624 396.85 0.188 4.77
10 15.5 393.7 0.25 6.35
20 15.376 390.55 0.312 7.92
Std 30 15.25 387.35 0.375 9.52
XS 40 15 381 0.5 12.7
60 14.688 373.08 0.656 16.66
80 14.232 361.49 0.844 22.45
100 13.938 354.03 1.031 26.19
120 13.562 344.47 1.219 30.96
140 13.124 333.35 1.438 36.52
160 12.812 325.42 1.594 40.49
18 450 18 457.2 5S 17.67 448.82 0.165 4.19
10S 17.624 447.65 0.188 4.77
10 17.5 444.5 0.25 6.35
20 17.376 441.35 0.312 7.92
Std 17.25 438.15 0.375 9.52
30 17.124 434.95 0.438 11.13
XS 17 431.8 0.5 12.7
40 16.876 427.65 0.562 14.27
60 16.5 419.1 0.75 19.05
80 16.124 409.55 0.938 23.82
100 15.688 398.48 1.156 29.36
120 15.25 387.35 1.375 34.92
140 14.876 377.85 1.562 39.67
160 14.438 366.73 1.781 45.24
20 500 20 508 5S 19.624 498.45 0.188 4.77
10S 19.564 496.93 0.218 5.54
10 19.5 495.3 0.25 6.35
Std 20 19.25 488.95 0.375 9.52
XS 30 19 482.6 0.5 12.7
40 18.812 477.82 0.594 15.09
60 18.376 466.75 0.812 20.62
80 17.938 455.63 1.031 26.19
100 17.438 442.93 1.281 32.54
120 17 431.8 1.5 38.1
140 16.5 419.1 1.75 44.45
160 16.062 407.97 1.969 50.01
22 550 22 558.8 5S 21.624 549.25 0.188 4.77
10S 21.564 547.73 0.218 5.54
10 21.5 546.1 0.25 6.35
Std 20 21.25 539.75 0.375 9.52
XS 30 21 533.4 0.5 12.7
40 20.812 528.62 0.594 15.09
60 20.25 514.35 0.875 22.22
80 19.75 501.65 1.125 28.57
100 19.25 488.95 1.375 34.92
120 18.75 476.25 1.625 41.27
140 18.25 463.55 1.875 47.62
160 17.75 450.85 2.125 53.97
24 600 24 609.6 5S 23.564 598.53 0.218 5.54
10 10S 23.5 596.9 0.25 6.35
Std 20 23.25 590.55 0.375 9.52
XS 23 584.2 0.599 12.7
30 22.876 581.05 0.562 14.27
40 22.624 574.65 0.688 17.48
60 22.062 560.37 0.969 24.61
80 21.562 547.67 1.219 30.96
100 20.938 531.83 1.531 38.89
120 20.376 517.55 1.812 46.02
140 19.876 504.85 2.062 52.37
160 19.312 490.92 2.344 59.54
26 650 26 660.4 10 25.376 644.55 0.312 7.92
Std 25.25 641.35 0.375 9.52
XS 20 25 635 0.5 12.7
28 700 28 711.2 10 27.376 697.35 0.312 7.92
Std 27.25 692.15 0.375 9.52
XS 20 27 685.8 0.5 12.7
30 26.75 679.45 0.625 15.87
30 750 30 762 5S 29.5 749.3 0.25 6.35
10 10S 29.376 746.15 0.312 7.92
Std 29.25 742.95 0.375 9.52
XS 20 29 736.6 0.5 12.7
30 28.759 730.25 0.625 15.87
32 800 32 812.8 10 31.376 796.95 0.312 7.92
Std 31.25 793.75 0.375 9.52
XS 20 31 787.4 0.5 12.7
30 30.75 781.05 0.65 15.87
40 30.624 777.85 0.688 17.47
34 850 34 863.6 10 33.312 846.12 0.344 8.74
Std 33.25 844.55 0.375 9.52
XS 20 33 838.2 0.5 12.7
30 32.75 831.85 0.625 15.87
40 22.624 828.65 0.688 17.47
36 900 36 914.4 10 35.376 898.55 0.312 7.92
Std 35.25 895.35 0.375 9.52
XS 20 35 889 0.5 12.7
30 34.75 882.65 0.625 15.87
40 34.5 876.3 0.75 19.05
42 1050 42 1066.8 Std 41.25 1047.75 0.375 9.52
XS 20 41 1041.4 0.5 12.7
30 40.75 1035.05 0.625 15.87
40 40.5 1028.7 0.75 19.05

Conclusion

An introductory article on pipes, different types of pipes, pipes sizes and Pipe Size Chart for commonly used pipe sizes. This Pipe Size Chart comes handy when working with pipes of different sizes to know about the outer diameter, inner diameter, wall thickness and many other important dimensions of a pipe.

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