NPS 1/4 Standard (STD) Pipe
0.540 in (13.7 mm) outside diameter on a 0.088 in (2.2 mm) wall, giving a 0.364 in (9.2 mm) bore and 0.42 lb/ft (0.63 kg/m) empty. ASME B36.10M.
- Nominal size
- NPS 1/4 (DN 8)
- Schedule
- Standard (STD)
- Outside diameter
- 0.540 in (13.7 mm)
- Wall thickness
- 0.088 in (2.2 mm)
- Inside diameter
- 0.364 in (9.2 mm)
- Weight, empty
- 0.42 lb/ft (0.63 kg/m)
- Weight, water filled
- 0.47 lb/ft (0.70 kg/m)
- Flow area
- 0.104 in² (67 mm²)
In NPS 1/4 this wall thickness is also designated Schedule 40. That is the same pipe under another name, not a different product — but the coincidence is specific to this size and does not hold across the range.
Every schedule in NPS 1/4
Dimensions are given in inches, with the millimetre equivalent beneath in grey.
| Schedule | Wall thickness | Inside diameter | Weight, empty | Water (US gal/ft) |
|---|---|---|---|---|
| Sch 5 | 0.0491.24 mm | 0.44211.23 mm | 0.260.38 kg/m | 0.008 |
| Sch 10 | 0.0651.65 mm | 0.41010.41 mm | 0.330.49 kg/m | 0.007 |
| Sch 40 | 0.0882.24 mm | 0.3649.25 mm | 0.420.63 kg/m | 0.005 |
| STD this page | 0.0882.24 mm | 0.3649.25 mm | 0.420.63 kg/m | 0.005 |
| Sch 80 | 0.1193.02 mm | 0.3027.67 mm | 0.540.80 kg/m | 0.004 |
| XS | 0.1193.02 mm | 0.3027.67 mm | 0.540.80 kg/m | 0.004 |
Weight is plain-end carbon steel, w = 10.6802 × t × (OD − t) lb/ft.
Common questions
What is the inside diameter of NPS 1/4 standard (std) pipe?
0.364 in (9.2 mm). The outside diameter is fixed at 0.540 in (13.7 mm) by ASME B36.10M, and the 0.088 in (2.2 mm) wall takes 0.176 in off it — 0.088 in from each side — leaving that bore.
How much does NPS 1/4 standard (std) pipe weigh?
0.42 lb/ft (0.63 kg/m) empty, as plain-end carbon steel. Full of water it comes to 0.47 lb/ft (0.70 kg/m), because the bore holds 0.005 US gallons per foot. One short ton of this pipe is about 4708 ft.
Does NPS 1/4 standard (std) pipe use special flanges or fittings?
No. Flanges and buttweld fittings are dimensioned from NPS, so NPS 1/4 hardware fits this pipe in any schedule. The one thing that does follow the schedule is the bore of a weld neck flange or a fitting end prep, which has to be 0.364 in (9.2 mm) to match.