NPS 18 Pipe Dimensions
Outside diameter 18.000 in (457.2 mm) — fixed across every schedule. 13 wall thicknesses from ASME B36.10M, with bore, plain-end weight and flow area for each.
- Nominal size
- NPS 18
- Metric designator
- DN 450
- Outside diameter
- 18.000 in (457.2 mm)
- Schedules listed
- 13
- Standard weight wall
- 0.375 in (9.5 mm)
- Extra strong wall
- 0.500 in (12.7 mm)
Every schedule in NPS 18
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| Schedule | Wall thickness | Inside diameter | Weight, empty | Flow area (in²) | Water (US gal/ft) |
|---|---|---|---|---|---|
| Sch 5 | 0.1654.19 mm | 17.670448.82 mm | 31.4346.77 kg/m | 245.22 | 12.739 |
| Sch 10 | 0.1884.78 mm | 17.624447.65 mm | 35.7653.22 kg/m | 243.95 | 12.673 |
| Sch 20 | 0.3127.92 mm | 17.376441.35 mm | 58.9487.71 kg/m | 237.13 | 12.319 |
| Sch 30 | 0.43811.13 mm | 17.124434.95 mm | 82.15122.26 kg/m | 230.30 | 11.964 |
| Sch 40 | 0.56214.27 mm | 16.876428.65 mm | 104.67155.76 kg/m | 223.68 | 11.620 |
| STD | 0.3759.52 mm | 17.250438.15 mm | 70.59105.05 kg/m | 233.71 | 12.141 |
| Sch 60 | 0.75019.05 mm | 16.500419.10 mm | 138.18205.63 kg/m | 213.82 | 11.108 |
| Sch 80 | 0.93823.83 mm | 16.124409.55 mm | 170.93254.37 kg/m | 204.19 | 10.607 |
| XS | 0.50012.70 mm | 17.000431.80 mm | 93.45139.07 kg/m | 226.98 | 11.791 |
| Sch 100 | 1.15629.36 mm | 15.688398.48 mm | 207.96309.48 kg/m | 193.30 | 10.041 |
| Sch 120 | 1.37534.92 mm | 15.250387.35 mm | 244.14363.32 kg/m | 182.65 | 9.489 |
| Sch 140 | 1.56239.67 mm | 14.876377.85 mm | 274.23408.09 kg/m | 173.80 | 9.029 |
| Sch 160 | 1.78145.24 mm | 14.438366.73 mm | 308.51459.11 kg/m | 163.72 | 8.505 |
Weight is calculated for carbon steel as w = 10.6802 × t × (OD − t) lb/ft and is the plain-end weight, excluding coatings, linings and fittings.
Standard weight does not coincide with any numbered schedule in this size. Extra strong does not coincide with a numbered schedule here.
This size, schedule by schedule
A page for each combination, with bore, weight, water capacity and the matching flange and fitting data.
This size in a schedule chart
Common questions
What is the outside diameter of NPS 18 pipe?
NPS 18 pipe has an outside diameter of 18.000 in (457.2 mm). That outside diameter is fixed: it is identical in every schedule, and only the wall thickness — and therefore the bore — changes from one schedule to the next.
How much does NPS 18 schedule 40 pipe weigh?
104.67 lb/ft (155.76 kg/m) as plain-end carbon steel, on a wall thickness of 0.562 in (14.3 mm).
What is the metric equivalent of NPS 18?
DN 450. DN is a dimensionless designator, not a measurement — DN 450 pipe does not measure 450 mm anywhere. Its actual outside diameter is 457.2 mm.