Nominal Pipe Size
A North American size designation (ASME). For NPS ⅛" to 12" the outside diameter is larger than the nominal size; from NPS 14" upward the OD equals the NPS – e.g. NPS 14 = 14.000" OD.
The Basics
Understanding Pipe Schedules
Pipe is ordered by nominal size and schedule – not by its actual diameter. Here is what those numbers mean.
Diameter Nominal
The metric (ISO) equivalent of NPS, in millimetres – e.g. NPS 2 = DN 50, NPS 6 = DN 150. The OD for a given NPS and DN is the same.
Schedule Number
Defines the wall thickness. For the same NPS, a higher schedule means a thicker wall, a smaller ID and a higher pressure rating – the OD stays the same.
STD, XS & XXS
Weight classes: Standard, Extra Strong and Double Extra Strong. STD equals Sch 40 up to NPS 10; XS equals Sch 80 up to NPS 8. Above those sizes they differ.
"S" Schedules
5S, 10S, 40S and 80S are stainless steel schedules from ASME B36.19M. 40S and 80S have the same wall as STD and XS respectively.
Useful Formulas
ID = OD − 2 × WT
Weight (kg/m) = 0.02466 × WT × (OD − WT)
Carbon steel, OD & WT in mm (density 7.85 g/cm³)
Pipe Schedule Chart
Wall thickness for each schedule. Hover or tap a value to highlight its size and schedule.
| NPS DN |
OD mm |
5S | 10S | 10 | 20 | 30 | STD 40S |
40 | 60 | XS 80S |
80 | 100 | 120 | 140 | 160 | XXS |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ⅛"DN 6 | 10.3 | – | 1.24 | 1.24 | – | 1.45 | 1.73 | 1.73 | – | 2.41 | 2.41 | – | – | – | – | – |
| ¼"DN 8 | 13.7 | – | 1.65 | 1.65 | – | 1.85 | 2.24 | 2.24 | – | 3.02 | 3.02 | – | – | – | – | – |
| ⅜"DN 10 | 17.1 | – | 1.65 | 1.65 | – | 1.85 | 2.31 | 2.31 | – | 3.20 | 3.20 | – | – | – | – | – |
| ½"DN 15 | 21.3 | 1.65 | 2.11 | 2.11 | – | 2.41 | 2.77 | 2.77 | – | 3.73 | 3.73 | – | – | – | 4.78 | 7.47 |
| ¾"DN 20 | 26.7 | 1.65 | 2.11 | 2.11 | – | 2.41 | 2.87 | 2.87 | – | 3.91 | 3.91 | – | – | – | 5.56 | 7.82 |
| 1"DN 25 | 33.4 | 1.65 | 2.77 | 2.77 | – | 2.90 | 3.38 | 3.38 | – | 4.55 | 4.55 | – | – | – | 6.35 | 9.09 |
| 1¼"DN 32 | 42.2 | 1.65 | 2.77 | 2.77 | – | 2.97 | 3.56 | 3.56 | – | 4.85 | 4.85 | – | – | – | 6.35 | 9.70 |
| 1½"DN 40 | 48.3 | 1.65 | 2.77 | 2.77 | – | 3.18 | 3.68 | 3.68 | – | 5.08 | 5.08 | – | – | – | 7.14 | 10.16 |
| 2"DN 50 | 60.3 | 1.65 | 2.77 | 2.77 | – | 3.18 | 3.91 | 3.91 | – | 5.54 | 5.54 | – | – | – | 8.74 | 11.07 |
| 2½"DN 65 | 73.0 | 2.11 | 3.05 | 3.05 | – | 4.78 | 5.16 | 5.16 | – | 7.01 | 7.01 | – | – | – | 9.53 | 14.02 |
| 3"DN 80 | 88.9 | 2.11 | 3.05 | 3.05 | – | 4.78 | 5.49 | 5.49 | – | 7.62 | 7.62 | – | – | – | 11.13 | 15.24 |
| 3½"DN 90 | 101.6 | 2.11 | 3.05 | 3.05 | – | 4.78 | 5.74 | 5.74 | – | 8.08 | 8.08 | – | – | – | – | 16.15 |
| 4"DN 100 | 114.3 | 2.11 | 3.05 | 3.05 | – | 4.78 | 6.02 | 6.02 | – | 8.56 | 8.56 | – | 11.13 | – | 13.49 | 17.12 |
| 5"DN 125 | 141.3 | 2.77 | 3.40 | 3.40 | – | – | 6.55 | 6.55 | – | 9.53 | 9.53 | – | 12.70 | – | 15.88 | 19.05 |
| 6"DN 150 | 168.3 | 2.77 | 3.40 | 3.40 | – | – | 7.11 | 7.11 | – | 10.97 | 10.97 | – | 14.27 | – | 18.26 | 21.95 |
| 8"DN 200 | 219.1 | 2.77 | 3.76 | 3.76 | 6.35 | 7.04 | 8.18 | 8.18 | 10.31 | 12.70 | 12.70 | 15.09 | 18.26 | 20.62 | 23.01 | 22.23 |
| 10"DN 250 | 273.0 | 3.40 | 4.19 | 4.19 | 6.35 | 7.80 | 9.27 | 9.27 | 12.70 | 12.70 | 15.09 | 18.26 | 21.44 | 25.40 | 28.58 | 25.40 |
| 12"DN 300 | 323.8 | 3.96 | 4.57 | 4.57 | 6.35 | 8.38 | 9.53 | 10.31 | 14.27 | 12.70 | 17.48 | 21.44 | 25.40 | 28.58 | 33.32 | 25.40 |
| 14"DN 350 | 355.6 | 3.96 | 4.78 | 6.35 | 7.92 | 9.53 | 9.53 | 11.13 | 15.09 | 12.70 | 19.05 | 23.83 | 27.79 | 31.75 | 35.71 | – |
| 16"DN 400 | 406.4 | 4.19 | 4.78 | 6.35 | 7.92 | 9.53 | 9.53 | 12.70 | 16.66 | 12.70 | 21.44 | 26.19 | 30.96 | 36.53 | 40.49 | – |
| 18"DN 450 | 457.0 | 4.19 | 4.78 | 6.35 | 7.92 | 11.13 | 9.53 | 14.27 | 19.05 | 12.70 | 23.83 | 29.36 | 34.93 | 39.67 | 45.24 | – |
| 20"DN 500 | 508.0 | 4.78 | 5.54 | 6.35 | 9.53 | 12.70 | 9.53 | 15.09 | 20.62 | 12.70 | 26.19 | 32.54 | 38.10 | 44.45 | 50.01 | – |
| 22"DN 550 | 559.0 | 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"DN 600 | 610.0 | 5.54 | 6.35 | 6.35 | 9.53 | 14.27 | 9.53 | 17.48 | 24.61 | 12.70 | 30.96 | 38.89 | 46.02 | 52.37 | 59.54 | – |
- All wall thickness values in mm; "–" = schedule not defined for that size.
- Values are nominal. Mill tolerance permits the wall to be up to 12.5% under nominal (e.g. ASTM A106, A312, A790).
- For weights per metre, use the calculator below or see our Weight Chart.
Pipe Calculator
Find ID & Weight per Metre
Choose a pipe size, schedule and material to get the outside diameter, wall thickness, inside diameter and theoretical weight – taken directly from the chart above.
- Weight = π × WT × (OD − WT) × density
- Theoretical, plain-end pipe – excludes coatings & tolerances
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