ASME B36.10M (welded and seamless wrought steel pipe) · DN 8
Outside diameter 0.540" (13.72 mm), wall 0.073" (1.85 mm), inside diameter 0.394" (10.02 mm), 0.36 lb per foot.
| Trade size | NPS 1/4 · DN 8 |
|---|---|
| Schedule | Schedule 30 |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 0.540" · 13.72 mm · designated 13.7 mm in the metric column |
| Wall thickness | 0.073" · 1.85 mm |
| Inside diameter | 0.394" · 10.02 mm |
| Weight, plain end | 0.36 lb/ft · 0.54 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 0.36 lb/ft here, 1.1% from the published 0.36 lb/ft. The published figure is the one printed above.
NPS 1/4 schedule 30 pipe measures 0.540 in (13.72 mm) across the outside with a 0.073 in wall, so the bore is 0.394 in (10.02 mm). That bore gives a flow area of 0.1219 in² and holds 0.006334 US gallons per foot (0.07866 litres per metre). The outside diameter is 7.4 times the wall, and the steel itself has a cross-section of 0.1071 in² and weighs 0.36 lb per foot plain end. One trade size up, NPS 3/8 in the same schedule carries 1.80 times the flow area.
Schedule 10 is the next lighter wall at NPS 1/4: 0.065 in, 0.008 in thinner, which opens the bore to 0.410 in and adds 8.3% to the flow area, for 8.3% less weight per foot.
Schedule 40 is the next heavier wall at NPS 1/4: 0.088 in, 0.015 in thicker, which narrows the bore to 0.364 in and cuts 15% from the flow area, for 17% more weight per foot.
Next trade size up in this schedule: NPS 3/8 schedule 30, bore 0.529 in.
| Flow area | 0.1219 in² |
|---|---|
| Capacity | 0.006334 US gal/ft · 0.07866 L/m |
| Metal area | 0.1071 in² |
| Moment of inertia | 0.002991 in⁴ |
| Section modulus | 0.01108 in³ |
| Radius of gyration | 0.1671 in |
| Outside surface | 0.1414 ft² per foot |
Plain geometry of a hollow circle with OD = 0.540 in and ID = 0.394 in: flow area π/4·ID², metal area π/4·(OD² − ID²), moment of inertia π/64·(OD⁴ − ID⁴), section modulus I ÷ (OD/2), radius of gyration √(I ÷ metal area), capacity flow area × 12 ÷ 231 (231 in³ to the US gallon). Nominal dimensions, so mill tolerance and corrosion allowance are not included.
Nominal Pipe Size is a label, not a measurement. NPS 1/4 pipe has an outside diameter of 0.540 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 30 the wall is 0.073 inches, so the bore comes out at 0.394 inches.
That is the practical consequence. Fittings, flanges, supports and threading dies are sized to the outside diameter, so they fit any schedule of the same trade size. Flow, pressure drop and anything that has to pass through the pipe depend on the inside diameter, which changes with every schedule. Order by trade size and schedule; work your hydraulics from the bore.
Same outside diameter of 0.540 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 10 · 10S | 0.065 | 0.410 | 0.33 |
| Schedule 40 · STD, 40S | 0.088 | 0.364 | 0.42 |
| Schedule 80 · XS, 80S | 0.119 | 0.302 | 0.54 |
0.073 inches (1.85 mm). The outside diameter is 0.540 inches (13.72 mm) whatever the schedule, so this wall leaves an inside diameter of 0.394 inches.
0.394 inches (10.02 mm). Inside diameter is outside diameter minus twice the wall: 0.540 - 2 x 0.073 = 0.394 inches.
No. NPS 1/4 is a trade size, not a measurement. The pipe measures 0.540 inches across the outside and 0.394 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
0.36 pounds per foot plain end (0.54 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
3 schedules at NPS 1/4 appear in only one of the published tables cross-checked for this section, so they are named rather than printed: 160, XXS, 5S. Everything shown above carries at least two independent sources.
This table runs from NPS 1/8 to NPS 24 and stops there. ASME B36.10M itself continues to NPS 80; those larger sizes are not carried here, so a size above NPS 24 is missing rather than undefined.
Dimensions are as defined by ASME B36.10M (welded and seamless wrought steel pipe). This site is an independent reference and is not affiliated with, endorsed by or approved by any standards body.
Every value on this page was cross-checked against 3 independent published sources:
Nearby sizes