A pipe's nominal size is a name, not a measurement. Pick the size and schedule to get the outside diameter, wall thickness, bore and weight per metre, or enter the diameter you measured to find which pipe it is.
| Outside diameter | 2.375 in · 60.3 mm |
|---|---|
| Wall thickness | 0.154 in · 3.91 mm |
| Inside diameter | 2.067 in · 52.48 mm |
| Weight (plain end) | 3.65 lb/ft · 5.44 kg/m |
| Inside volume | 2.16 L/m |
| Weight of 20 ft | 73.1 lb · 33.1 kg |
| Sch 10 | 0.109 in | 3.93 kg/m |
|---|---|---|
| Sch 40 | 0.154 in | 5.44 kg/m |
| Sch 80 | 0.218 in | 7.48 kg/m |
| Sch 160 | 0.344 in | 11.11 kg/m |
| STD | 0.154 in | 5.44 kg/m |
| XS | 0.218 in | 7.48 kg/m |
| XXS | 0.436 in | 13.44 kg/m |
Dimensions from ASME B36.10M (carbon and alloy steel) and B36.19M (stainless). Sizes a source table leaves blank are shown as —. Mill tolerance on the wall is typically −12.5%.
Weight = π × (OD − wall) × wall × 7.85 ÷ 1,000 kg/m, plain end, no coating. For PVC or copper the sizes may match but the weight does not.
| NPS | DN | OD in | OD mm | Sch 10 | Sch 40 | Sch 80 | Sch 160 | STD | XS | XXS |
|---|---|---|---|---|---|---|---|---|---|---|
| ⅛ | 6 | 0.405 | 10.3 | 0.049 | 0.068 | 0.095 | — | 0.068 | 0.095 | — |
| ¼ | 8 | 0.540 | 13.7 | 0.065 | 0.088 | 0.119 | — | 0.088 | 0.119 | — |
| ⅜ | 10 | 0.675 | 17.1 | 0.065 | 0.091 | 0.126 | — | 0.091 | 0.126 | — |
| ½ | 15 | 0.840 | 21.3 | 0.083 | 0.109 | 0.147 | 0.188 | 0.109 | 0.147 | 0.294 |
| ¾ | 20 | 1.050 | 26.7 | 0.083 | 0.113 | 0.154 | 0.219 | 0.113 | 0.154 | 0.308 |
| 1 | 25 | 1.315 | 33.4 | 0.109 | 0.133 | 0.179 | 0.250 | 0.133 | 0.179 | 0.358 |
| 1¼ | 32 | 1.660 | 42.2 | 0.109 | 0.140 | 0.191 | 0.250 | 0.140 | 0.191 | 0.382 |
| 1½ | 40 | 1.900 | 48.3 | 0.109 | 0.145 | 0.200 | 0.281 | 0.145 | 0.200 | 0.400 |
| 2 | 50 | 2.375 | 60.3 | 0.109 | 0.154 | 0.218 | 0.344 | 0.154 | 0.218 | 0.436 |
| 2½ | 65 | 2.875 | 73.0 | 0.120 | 0.203 | 0.276 | 0.375 | 0.203 | 0.276 | 0.552 |
| 3 | 80 | 3.500 | 88.9 | 0.120 | 0.216 | 0.300 | 0.438 | 0.216 | 0.300 | 0.600 |
| 3½ | 90 | 4.000 | 101.6 | 0.120 | 0.226 | 0.318 | — | 0.226 | 0.318 | — |
| 4 | 100 | 4.500 | 114.3 | 0.120 | 0.237 | 0.337 | 0.531 | 0.237 | 0.337 | 0.674 |
| 5 | 125 | 5.563 | 141.3 | 0.134 | 0.258 | 0.375 | 0.625 | 0.258 | 0.375 | 0.750 |
| 6 | 150 | 6.625 | 168.3 | 0.134 | 0.280 | 0.432 | 0.719 | 0.280 | 0.432 | 0.864 |
| 8 | 200 | 8.625 | 219.1 | 0.148 | 0.322 | 0.500 | 0.906 | 0.322 | 0.500 | 0.875 |
| 10 | 250 | 10.750 | 273.0 | 0.165 | 0.365 | 0.594 | 1.125 | 0.365 | 0.500 | 1.000 |
| 12 | 300 | 12.750 | 323.8 | 0.180 | 0.406 | 0.688 | 1.312 | 0.375 | 0.500 | 1.000 |
| 14 | 350 | 14.000 | 355.6 | 0.250 | 0.438 | 0.750 | 1.406 | 0.375 | 0.500 | — |
| 16 | 400 | 16.000 | 406.4 | 0.250 | 0.500 | 0.844 | 1.594 | 0.375 | 0.500 | — |
| 18 | 450 | 18.000 | 457.0 | 0.250 | 0.562 | 0.938 | 1.781 | 0.375 | 0.500 | — |
| 20 | 500 | 20.000 | 508.0 | 0.250 | 0.594 | 1.031 | 1.969 | 0.375 | 0.500 | — |
| 24 | 600 | 24.000 | 610.0 | 0.250 | 0.688 | 1.219 | 2.344 | 0.375 | 0.500 | — |
NPS and DN, outside diameter, wall and schedule on a photo of your own pipe or fitting, so the buyer does not have to translate between standards.
Steel pipe sizes have three numbers that are easy to mix up. The nominal size (NPS in inches, DN in millimetres) names the pipe. The outside diameter is fixed for each nominal size. The schedule sets the wall thickness, so a thicker wall makes the bore smaller, not the pipe bigger.
| NPS (DN) | OD mm (in) | Sch 40 wall / ID mm | Sch 40 kg/m | Sch 80 wall / ID mm | Sch 80 kg/m |
|---|---|---|---|---|---|
| ½ (DN 15) | 21.3 (0.840) | 2.77 / 15.76 | 1.27 | 3.73 / 13.84 | 1.62 |
| 1 (DN 25) | 33.4 (1.315) | 3.38 / 26.64 | 2.50 | 4.55 / 24.30 | 3.24 |
| 2 (DN 50) | 60.3 (2.375) | 3.91 / 52.48 | 5.44 | 5.54 / 49.22 | 7.48 |
| 4 (DN 100) | 114.3 (4.500) | 6.02 / 102.26 | 16.08 | 8.56 / 97.18 | 22.32 |
| 6 (DN 150) | 168.3 (6.625) | 7.11 / 154.08 | 28.26 | 10.97 / 146.36 | 42.56 |
| 8 (DN 200) | 219.1 (8.625) | 8.18 / 202.74 | 42.55 | 12.70 / 193.70 | 64.64 |
Carbon steel, plain end, 7.85 g/cm³. The full chart for every size and schedule is under the calculator. PVC Schedule 40 and 80 pipe (ASTM D1785) uses the same outside diameters and the same schedule walls — 2 in Sch 40 PVC is 2.375 in OD with a 0.154 in minimum wall — so the size columns apply; the weights do not.
Related: pipe and fitting dimensions: NPS, DN, schedule and OD · Schedule 40 vs Schedule 80 · PVC pipe sizes · metal weight calculator
They are two names for the same pipe size: NPS is the North American designation in inches, DN the metric one. NPS 2 is DN 50, NPS 4 is DN 100. Neither is a measurement; the outside diameter for both is fixed by the standard, 60.3 mm for NPS 2.
It depends on the size: 2.77 mm at NPS ½, 3.91 mm at NPS 2, 6.02 mm at NPS 4 and 8.18 mm at NPS 8. Schedule numbers keep the pressure rating roughly constant across sizes, so the wall grows with the diameter.
Up to NPS 10, yes. From NPS 12 they differ: 40S stays at 9.53 mm while Sch 40 is 10.31 mm at NPS 12 and 11.13 mm at NPS 14. The S schedules come from ASME B36.19M for stainless pipe.
Measure the OD and pick the nearest standard value: 21.3 mm is NPS ½, 33.4 mm NPS 1, 60.3 mm NPS 2, 114.3 mm NPS 4. Use "By measured OD" above. If nothing is within a few millimetres, the pipe probably follows a metric tube or copper standard.
π × (OD − wall) × wall × density ÷ 1,000, with OD and wall in mm. For carbon steel that is 0.0246615 × (OD − wall) × wall, the formula in ASME B36.10M: NPS 2 Sch 40 is 0.0246615 × 56.39 × 3.91 = 5.44 kg/m.
