Nominal Pipe Size NPS
Nominal Pipe Size (NPS) is a American standard sizes for pipes used for high or low pressure and temperature. Pipe size is specified with two non-dimensional numbers: a nominal pipe size (Nominal Pipe Size) based on inches, and a schedule (Sched. or Sch.). Nominal Pipe Size is often incorrectly called National Pipe Size, due to confusion with national pipe thread (NPT). The European designation equivalent to Nominal Pipe Size is DN (diamètre nominal/nominal diameter), in which sizes are measured in millimetres.The term NB (nominal bore) is also frequently used interchangeably with Nominal Pipe Size. According to ASME B36.10 and ASME B 36.19.
- NPS Nominal Pipe Size / Pipe Schdule ASME B36.10 and ASME B 36.19.
- Nominal Pipe Size 1/8 to Nominal Pipe Size 3½
- Nominal Pipe Size 4 to Nominal Pipe Size 9
- Nominal Pipe Size10 to Nominal Pipe Size 24
- NPS Nominal Pipe Size Remark
- NPS Nominal Pipe Size Application
- Download ASME B36.10 and ASME B 36.19 in PDF
- NPS Nominal Pipe Size Related Links
NPS Nominal Pipe Size / Pipe Schdule ASME B36.10 and ASME B 36.19.
| DN | OD inch | OD mm | SCH5S mm | SCH10S mm | SCH10 mm | SCH20 mm | SCH30 mm | STD mm | SCH40S mm | SCH40 mm | SCH60 mm | XS mm | SCH80S mm | SCH80 mm | SCH100 mm | SCH120 mm | SCH140 mm | SCH160 mm | XXS mm | |
| 1/8 | 6 | 0.405 | 10.3 | 1.24 | 1.24 | 1.45 | 1.73 | 1.73 | 1.73 | 2.41 | 2.41 | 2.41 | ||||||||
| 1/4 | 8 | 0.540 | 13.7 | 1.65 | 1.65 | 1.85 | 2.24 | 2.24 | 2.24 | 3.02 | 3.02 | 3.02 | ||||||||
| 3/8 | 10 | 0.675 | 17.1 | 1.65 | 1.65 | 1.85 | 2.31 | 2.31 | 2.31 | 3.20 | 3.20 | 3.20 | ||||||||
| 1/2 | 15 | 0.840 | 21.3 | 1.65 | 2.11 | 2.11 | 2.41 | 2.77 | 2.77 | 2.77 | 3.73 | 3.73 | 3.73 | 4.78 | 7.47 | |||||
| 3/4 | 20 | 1.050 | 26.7 | 1.65 | 2.11 | 2.11 | 2.41 | 2.87 | 2.87 | 2.87 | 3.91 | 3.91 | 3.91 | 5.56 | 7.82 | |||||
| 1 | 25 | 1.315 | 33.4 | 1.65 | 2.77 | 2.77 | 2.90 | 3.38 | 3.38 | 3.38 | 4.55 | 4.55 | 4.55 | 6.35 | 9.09 | |||||
| 1 ¼ | 32 | 1.660 | 42.2 | 1.65 | 2.77 | 2.77 | 2.97 | 3.56 | 3.56 | 3.56 | 4.85 | 4.85 | 4.85 | 6.35 | 9.70 | |||||
| 1 ½ | 40 | 1.900 | 48.3 | 1.65 | 2.77 | 2.77 | 3.18 | 3.68 | 3.68 | 3.68 | 5.08 | 5.08 | 5.08 | 7.14 | 10.15 | |||||
| 2 | 50 | 2.375 | 60.3 | 1.65 | 2.77 | 2.77 | 3.18 | 3.91 | 3.91 | 3.91 | 5.54 | 5.54 | 5.54 | 8.74 | 11.07 | |||||
| 2 ½ | 65 | 2.875 | 73 | 2.11 | 3.05 | 3.05 | 4.78 | 5.16 | 5.16 | 5.16 | 7.01 | 7.01 | 7.01 | 9.53 | 14.02 | |||||
| 3 | 80 | 3.500 | 88.9 | 2.11 | 3.05 | 3.05 | 4.78 | 5.49 | 5.49 | 5.49 | 7.62 | 7.62 | 7.62 | 11.13 | 15.24 | |||||
| 3 ½ | 90 | 4.000 | 101.6 | 2.11 | 3.05 | 3.05 | 4.78 | 5.74 | 5.74 | 5.74 | 8.08 | 8.08 | 8.08 | |||||||
| 4 | 100 | 4.500 | 114.3 | 2.11 | 3.05 | 3.05 | 4.78 | 6.02 | 6.02 | 6.02 | 8.56 | 8.56 | 8.56 | 11.13 | 13.49 | 17.12 | ||||
| 5 | 125 | 5.563 | 141.3 | 2.77 | 3.40 | 3.40 | 6.55 | 6.55 | 6.55 | 9.53 | 9.53 | 9.53 | 12.70 | 15.88 | 19.05 | |||||
| 6 | 150 | 6.625 | 168.3 | 2.77 | 3.40 | 3.40 | 7.11 | 7.11 | 7.11 | 10.97 | 10.97 | 10.97 | 14.27 | 18.26 | 21.95 | |||||
| 8 | 200 | 8.625 | 219.1 | 2.77 | 3.76 | 3.76 | 6.35 | 7.04 | 8.18 | 8.18 | 8.18 | 10.31 | 12.70 | 12.70 | 12.70 | 15.09 | 18.26 | 20.62 | 23.01 | 22.23 |
| 10 | 250 | 10.750 | 273.0 | 3.40 | 4.19 | 4.19 | 6.35 | 7.80 | 9.27 | 9.27 | 9.27 | 12.70 | 12.70 | 12.70 | 15.09 | 18.26 | 21.44 | 25.40 | 28.58 | 25.40 |
| 12 | 300 | 12.750 | 323.8 | 3.96 | 4.57 | 4.57 | 6.35 | 8.38 | 9.53 | 9.53 | 10.31 | 14.27 | 12.70 | 12.70 | 17.48 | 21.44 | 25.40 | 28.58 | 33.32 | 25.40 |
| 14 | 350 | 14.000 | 355.6 | 3.96 | 4.78 | 6.35 | 7.92 | 9.53 | 9.53 | 9.53 | 11.13 | 15.09 | 12.70 | 12.70 | 19.05 | 23.83 | 27.79 | 31.75 | 35.71 | |
| 16 | 400 | 16.000 | 406.4 | 4.19 | 4.78 | 6.35 | 7.92 | 9.53 | 9.53 | 9.53 | 12.70 | 16.66 | 12.70 | 12.70 | 21.44 | 26.19 | 30.96 | 36.53 | 40.49 | |
| 18 | 450 | 18.000 | 457.2 | 4.19 | 4.78 | 6.35 | 7.92 | 11.13 | 9.53 | 9.53 | 14.27 | 19.05 | 12.70 | 12.70 | 23.83 | 29.36 | 34.93 | 39.67 | 45.24 | |
| 20 | 500 | 20.000 | 508 | 4.78 | 5.54 | 6.35 | 9.53 | 12.70 | 9.53 | 9.53 | 15.09 | 20.62 | 12.70 | 12.70 | 26.19 | 32.54 | 38.10 | 44.45 | 50.01 | |
| 22 | 550 | 22.000 | 558.8 | 4.78 | 5.54 | 6.35 | 9.53 | 12.70 | 9.53 | 22.23 | 12.70 | 28.58 | 34.93 | 41.28 | 47.63 | 53.98 | ||||
| 24 | 600 | 24.000 | 609.6 | 5.54 | 6.35 | 6.35 | 9.53 | 14.27 | 9.53 | 9.53 | 17.48 | 24.61 | 12.70 | 12.70 | 30.96 | 38.89 | 46.02 | 52.37 | 59.54 | |
| 26 | 650 | 26.000 | 660.4 | 7.92 | 12.70 | 9.53 | 12.70 | |||||||||||||
| 28 | 700 | 28.000 | 711.2 | 7.92 | 12.70 | 15.88 | 9.53 | 12.70 | ||||||||||||
| 30 | 750 | 30.000 | 762 | 6.35 | 7.92 | 7.92 | 12.70 | 15.88 | 9.53 | 12.70 | ||||||||||
| 32 | 800 | 32.000 | 812.8 | 7.92 | 12.70 | 15.88 | 9.53 | 17.48 | 12.70 | |||||||||||
| 34 | 850 | 34.000 | 863.6 | 7.92 | 12.70 | 15.88 | 9.53 | 17.48 | 12.70 | |||||||||||
| 36 | 900 | 36.000 | 914.4 | 7.92 | 12.70 | 15.88 | 9.53 | 19.05 | 12.70 | |||||||||||
| 38 | 950 | 38.000 | 965.2 | 9.53 | 12.70 | |||||||||||||||
| 40 | 1000 | 40.000 | 1016 | 9.53 | 12.70 | |||||||||||||||
| 42 | 1050 | 42.000 | 1066.8 | 9.53 | 12.70 |
SCH5S is same with SCH5.
Nominal Pipe Size 1/8 to Nominal Pipe Size 3½
| Nominal Pipe Size | DN | OD inches(mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) |
| — | — | — | SCH 5 | SCH 10 | SCH 30 | SCH 40/STD | SCH 80 | SCH 120 | SCH 160 | XXS |
| ⅛ | 6 | 0.405 in (10.29 mm) | 0.035 in (0.889 mm) | 0.049 in (1.245 mm) | 0.057 in (1.448 mm) | 0.068 in (1.727 mm) | 0.095 in (2.413 mm) | — | — | — |
| ¼ | 8 | 0.540 in (13.72 mm) | 0.049 in (1.245 mm) | 0.065 in (1.651 mm) | 0.073 in (1.854 mm) | 0.088 in (2.235 mm) | 0.119 in (3.023 mm) | — | — | — |
| ⅜ | 10 | 0.675 in (17.15 mm) | 0.049 in (1.245 mm) | 0.065 in (1.651 mm) | 0.073 in (1.854 mm) | 0.091 in (2.311 mm) | 0.126 in (3.200 mm) | — | — | — |
| ½ | 15 | 0.840 in (21.34 mm) | 0.065 in (1.651 mm) | 0.083 in (2.108 mm) | — | 0.109 in (2.769 mm) | 0.147 in (3.734 mm) | — | 4.78mm | 0.294 in (7.47 mm) |
| ¾ | 20 | 1.050 in (26.67 mm) | 0.065 in (1.651 mm) | 0.083 in (2.108 mm) | 2.41mm | 0.113 in (2.870 mm) | 0.154 in (3.912 mm) | — | 5.56mm | 0.308 in (7.823 mm) |
| 1 | 25 | 1.315 in (33.40 mm) | 0.065 in (1.651 mm) | 0.109 in (2.769 mm) | 2.90mm | 0.133 in (3.378 mm) | 0.179 in (4.547 mm) | — | 6.35mm | 0.358 in (9.093 mm) |
| 1 ¼ | 32 | 1.660 in (42.16 mm) | 0.065 in (1.651 mm) | 0.109 in (2.769 mm) | 0.117 in (2.972 mm) | 0.140 in (3.556 mm) | 0.191 in (4.851 mm) | — | 6.35mm | 0.382 in (9.703 mm) |
| 1 ½ | 40 | 1.900 in (48.26 mm) | 0.065 in (1.651 mm) | 0.109 in (2.769 mm) | 0.125 in (3.175 mm) | 0.145 in (3.683 mm) | 0.200 in (5.080 mm) | — | 7.14mm | 0.400 in (10.160 mm) |
| 2 | 50 | 2.375 in (60.33 mm) | 0.065 in (1.651 mm) | 0.109 in (2.769 mm) | 0.125 in (3.175 mm) | 0.154 in (3.912 mm) | 0.218 in (5.537 mm) | 0.250 in (6.350 mm) | 8.74mm | 0.436 in (11.074 mm) |
| 2 ½ | 65 | 2.875 in (73.02 mm) | 0.083 in (2.108 mm) | 0.120 in (3.048 mm) | 0.188 in (4.775 mm) | 0.203 in (5.156 mm) | 0.276 in (7.010 mm) | 0.300 in (7.620 mm) | 0.344 in (8.738 mm) | 0.552 in (14.021 mm) |
| 3 | 80 | 3.500 in (88.90 mm) | 0.083 in (2.108 mm) | 0.120 in (3.048 mm) | 0.188 in (4.775 mm) | 0.216 in (5.486 mm) | 0.300 in (7.620 mm) | 0.350 in (8.890 mm) | 0.438 in (11.13 mm) | 0.600 in (15.240 mm) |
| 3 ½ | 90 | 4.000 in (101.60 mm) | 0.083 in (2.108 mm) | 0.120 in (3.048 mm) | 0.188 in (4.775 mm) | 0.226 in (5.740 mm) | 0.318 in (8.077 mm) | — | — | 0.636 in (16.154 mm) |
Nominal Pipe Size 4 to Nominal Pipe Size 9
| NPS | DN mm | OD inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) |
| — | — | — | SCH 5 | SCH 10 | SCH 20 | SCH 30 | SCH 40/STD | SCH 60 | SCH 80 | SCH 100 | SCH 120 | SCH 140 | SCH 160 |
| 4 | 100 | 4.500 in (114.30 mm) | 0.083 in (2.108 mm) | 0.120 in (3. 048 mm) | — | 0.188 in (4. 775 mm) | 0.237 in (6.02 mm) | 0.281 in (7.137 mm) | 0.337 in (8.560 mm) | — | 0.437 in (11.13 mm) | — | 0.531 in (13.49 mm) |
| 4 ½ | 115 | 5.000 in (127.00 mm) | — | — | — | — | 0.247 in (6.274 mm) | — | 0.355 in (9.017 mm) | — | — | — | — |
| 5 | 125 | 5.563 in (141.30 mm) | 0.109 in (2.769 mm) | 0.134 in (3.404 mm) | — | — | 0.258 in (6.553 mm) | — | 0.375 in (9.525 mm) | — | 0.500 in (12.70 mm) | — | 0.625 in (15.875 mm) |
| 6 | 150 | 6.625 in (168.27 mm) | 0.109 in (2.769 mm) | 0.134 in (3.404 mm) | — | — | 0.280 in (7.112 mm) | — | 0.432 in (10.973 mm) | — | 0.562 in (14.27 mm) | — | 0.719 in (18.263 mm) |
| 8 | 200 | 8.625 in (219.08 mm) | 0.109 in (2.769 mm) | 0.148 in (3.759 mm) | 0.250 in (6. 35 mm) | 0.277 in (7. 036 mm) | 0.322 in (8.179 mm) | 0.406 in (10. 312 mm) | 0.500 in (12.70 mm) | 0.593 in (15. 09 mm) | 0.718 in (18.2 6mm) | 0.812 in (20. 62mm) | 0.906 in (23.01 mm) |
Nominal Pipe Size10 to Nominal Pipe Size 24
| Nominal Pipe Size | DN mm | OD inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) |
| — | — | — | SCH 5s | SCH 5 | SCH 10s | SCH 10 | SCH 20 | SCH 30 |
| 10 | 250 | 10.75 in (273.05 mm) | 0.134 in (3.404 mm) | 0.134 in (3.404 mm) | 0.165 in (4.191 mm) | 0.165 in (4.191 mm) | 0.250 in (6.350 mm) | 0.307 in (7.798 mm) |
| 12 | 300 | 12.75 in (323.85 mm) | 0.156 in (3.962 mm) | 0.165 in (4.191 mm) | 0.180 in (4.572 mm) | 0.180 in (4.572 mm) | 0.250 in (6.350 mm) | 0.330 in (8.382 mm) |
| 14 | 350 | 14.00 in (355.60 mm) | 0.156 in (3.962 mm) | 0.156 in (3.962 mm) | 0.188 in (4.775 mm) | 0.250 in (6.350 mm) | 0.312 in (7.925 mm) | 0.375 in (9.525 mm) |
| 16 | 400 | 16.00 in (406.40 mm) | 0.165 in (4.191 mm) | 0.165 in (4.191 mm) | 0.188 in (4.775 mm) | 0.250 in (6.350 mm) | 0.312 in (7.925 mm) | 0.375 in (9.525 mm) |
| 18 | 450 | 18.00 in (457.20 mm) | 0.165 in (4.191 mm) | 0.165 in (4.191 mm) | 0.188 in (4.775 mm) | 0.250 in (6.350 mm) | 0.312 in (7.925 mm) | 0.437 in (11.100 mm) |
| 20 | 500 | 20.00 in (508.00 mm) | 0.188 in (4.775 mm) | 0.188 in (4.775 mm) | 0.218 in (5.537 mm) | 0.250 in (6.350 mm) | 0.375 in (9.525 mm) | 0.500 in (12.700 mm) |
| 24 | 600 | 24.00 in (609.60 mm) | 0.218 in (5.537 mm) | 0.218 in (5.537 mm) | 0.250 in (6.350 mm) | 0.250 in (6.350 mm) | 0.375 in (9.525 mm) | 0.562 in (14.275 mm) |
| Nominal Pipe Size | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) | WT inches (mm) |
| — | SCH 40s | SCH 40 | SCH 60 | SCH 80s | SCH 80 | SCH 100 | SCH 120 | SCH 140 | SCH 160 |
| 10 | 0.365 in (9.271 mm) | 0.365 in (9.271 mm) | 0.500 in (12.700 mm) | 0.500 in (12.700 mm) | 0.593 in (15.062 mm) | 0.718 in (18.237 mm) | 0.843 in (21.412 mm) | 1.000 in (25.400 mm) | 1.125 in (28.575 mm) |
| 12 | 0.375 in (9.525 mm) | 0.406 in (10.312 mm) | 0.500 in (12.700 mm) | 0.500 in (12.700 mm) | 0.687 in (17.450 mm) | 0.843 in (21.412 mm) | 1.000 in (25.400 mm) | 1.125 in (28.575 mm) | 1.312 in (33.325 mm) |
| 14 | 0.375 in (9.525 mm) | 0.437 in (11.100 mm) | 0.593 in (15.062 mm) | 0.500 in (12.700 mm) | 0.750 in (19.050 mm) | 0.937 in (23.800 mm) | 1.093 in (27.762 mm) | 1.250 in (31.750 mm) | 1.406 in (35.712 mm) |
| 16 | 0.375 in (9.525 mm) | 0.500 in (12.700 mm) | 0.656 in (16.662 mm) | 0.500 in (12.700 mm) | 0.843 in (21.412 mm) | 1.031 in (26.187 mm) | 1.218 in (30.937 mm) | 1.437 in (36.500 mm) | 1.593 in (40.462 mm) |
| 18 | 0.375 in (9.525 mm) | 0.562 in (14.275 mm) | 0.750 in (19.050 mm) | 0.500 in (12.700 mm) | 0.937 in (23.800 mm) | 1.156 in (29.362 mm) | 1.375 in (34.925 mm) | 1.562 in (39.675 mm) | 1.781 in (45.237 mm) |
| 20 | 0.375 in (9.525 mm) | 0.593 in (15.062 mm) | 0.812 in (20.625 mm) | 0.500 in (12.700 mm) | 1.031 in (26.187 mm) | 1.280 in (32.512 mm) | 1.500 in (38.100 mm) | 1.750 in (44.450 mm) | 1.968 in (49.987 mm) |
| 24 | 0.375 in (9.525 mm) | 0.687 in (17.450 mm) | 0.968 in (24.587 mm) | 0.500 in (12.700 mm) | 1.218 in (30.937 mm) | 1.531 in (38.887 mm) | 1.812 in (46.025 mm) | 2.062 in (52.375 mm) | 2.343 in (59.512 mm) |
NPS Nominal Pipe Size Remark
Schedule 40 and 80 approaching the STD and XS and are in many cases the same.
From NPS 12 and above the wall thickness between schedule 40 and STD are different, from NPS 10 and above the wall thickness between schedule 80 and XS are different.
Schedule 10, 40 and 80 are in many cases the same as schedule 10S, 40S and 80S.
But watch out, from NPS 12 – NPS 22 the wall thicknesses in some cases are different. Pipes with suffix “S” have in that range thinner wall ticknesses.
ASME B36.19 does not cover all pipe sizes. Therefore, the dimensional requirements of ASME B36.10 apply to stainless steel pipe of the sizes and schedules not covered by ASME B36.19.
NPS Nominal Pipe Size Application
Based on the NPS and schedule of a pipe, the pipe outside diameter (OD) and wall thickness can be obtained from reference tables such as those below, which are based on ASME standards B36.10M and B36.19M. For example, NPS 14 Sch 40 has an OD of 14 inches and a wall thickness of 0.437 inches. However the NPS and OD values are not always equal, which can create confusion.
For NPS ⅛ to 12 inches, the NPS and OD values are different. For example, the OD of an NPS 12 pipe is actually 12.75 inches. To find the actual OD for each NPS value, refer to the tables below. (Note that for tubing, the size is always the actual OD.)
For NPS 14 inches and up, the NPS and OD values are equal. In other words, an NPS 14 pipe is actually 14 inches OD.
The reason for the discrepancy for NPS ⅛ to 12 inches is that these NPS values were originally set to give the same inside diameter (ID) based on wall thicknesses standard at the time. However, as the set of available wall thicknesses evolved, the ID changed and NPS became only indirectly related to ID and OD.
For a given NPS, the OD stays fixed and the wall thickness increases with schedule. For a given schedule, the OD increases with NPS while the wall thickness stays constant or increases. Using equations and rules in ASME B31.3 Process Piping, it can be shown that pressure rating decreases with increasing NPS and constant schedule.[4]
Some specifications use pipe schedules called standard wall (STD), extra strong (XS), and double extra strong (XXS), although these actually belong to an older system called iron pipe size (IPS). The IPS number is the same as the NPS number. STD is identical to SCH 40S, and 40S is identical to 40 for NPS 1/8 to NPS 10, inclusive. XS is identical to SCH 80S, and 80S is identical to 80 for NPS 1/8 to NPS 8, inclusive. Different definitions exist for XXS, but it is generally thicker than schedule 160.
The “S” designation, for example “NPS Sch 10S”, most often indicates stainless steel pipes.
The terms Nominal Bore (NB) and Nominal Diameter (DN) are also frequently used interchangeably with Nominal Pipe Size (NPS). Nominal Bore (NB) is European Designation equivalent to NPS. For NPS 5 and larger, the Nominal Diameter (DN) is equal to the NPS multiplied by 25.
Initially there are only three pipe wall thicknesses in use –
- Standard (STD)
- Extra Strong (XS)
- Double Extra Strong (XXS)
NPS Nominal Pipe Size Related link
Pipe Schedule
Stainless Steel Tube Size
ASME B36.10M Welded and Seamless Wrought Steel Pipe
ASME B36.19M Stainless Steel Pipe
Pipe Schedule
Gauge Size
Nominal Pipe Size
Stainless Steel Pipe Dimensions
Sheet Metal Gauge
Stainless Steel Pipe Size
Stainless Steel Tube Size
ANSI Standard Pipe Chart
Inch to mm Chart
B.W.G. – Birmingham Wire Gauge
A.S.W.G. American Standard Wire Gauge
Gauge Tolerances of Stainless Steel
Conversion Table of Temperatue, Length,Mass,Pressure
NPS-Nominal-Pipe-Size and DN – Diametre Nominal
ISO Tolerances For FastenersISO Tolerance Chart|Machining Process associated with ISO IT Tolerance GradeStainless Steel Thickness Weight Table
Galvanized Structural Steel Thickness Weight Table
Cold Rolled Steel Thickness Weight Table
Hot Rolled Steel Thickness Weight Table