ASME B36.10M (welded and seamless wrought steel pipe) · DN 250
Outside diameter 10.750" (273.05 mm), wall 0.844" (21.44 mm), inside diameter 9.062" (230.17 mm), 89.38 lb per foot.
| Trade size | NPS 10 · DN 250 |
|---|---|
| Schedule | Schedule 120 |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 10.750" · 273.05 mm · designated 273 mm in the metric column |
| Wall thickness | 0.844" · 21.44 mm |
| Inside diameter | 9.062" · 230.17 mm |
| Weight, plain end | 89.38 lb/ft · 133.01 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 89.29 lb/ft here, 0.1% from the published 89.38 lb/ft. The published figure is the one printed above.
NPS 10 schedule 120 pipe measures 10.750 in (273.05 mm) across the outside with a 0.844 in wall, so the bore is 9.062 in (230.17 mm). That bore gives a flow area of 64.50 in² and holds 3.350 US gallons per foot (41.61 litres per metre). The outside diameter is 12.7 times the wall, and the steel itself has a cross-section of 26.27 in² and weighs 89.38 lb per foot plain end. One trade size up, NPS 12 in the same schedule carries 1.41 times the flow area.
Schedule 100 is the next lighter wall at NPS 10: 0.719 in, 0.125 in thinner, which opens the bore to 9.312 in and adds 5.6% to the flow area, for 14% less weight per foot.
Double extra strong (XXS) is the next heavier wall at NPS 10: 1.000 in, 0.156 in thicker, which narrows the bore to 8.750 in and cuts 6.8% from the flow area, for 17% more weight per foot.
Next trade size up in this schedule: NPS 12 schedule 120, bore 10.750 in.
| Flow area | 64.50 in² |
|---|---|
| Capacity | 3.350 US gal/ft · 41.61 L/m |
| Metal area | 26.27 in² |
| Moment of inertia | 324.5 in⁴ |
| Section modulus | 60.38 in³ |
| Radius of gyration | 3.515 in |
| Outside surface | 2.814 ft² per foot |
Plain geometry of a hollow circle with OD = 10.750 in and ID = 9.062 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 10 pipe has an outside diameter of 10.750 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 120 the wall is 0.844 inches, so the bore comes out at 9.062 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 10.750 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.134 | 10.482 | 15.21 |
| Schedule 10 · 10S | 0.165 | 10.420 | 18.67 |
| Schedule 20 | 0.250 | 10.250 | 28.06 |
| Schedule 30 | 0.307 | 10.136 | 34.27 |
| Schedule 40 · STD, 40S | 0.365 | 10.020 | 40.52 |
| Schedule 80 | 0.594 | 9.562 | 64.49 |
| Schedule 100 | 0.719 | 9.312 | 77.10 |
| Schedule 160 | 1.125 | 8.500 | 115.75 |
| Extra strong (XS) · 60, 80S | 0.500 | 9.750 | 54.79 |
| Double extra strong (XXS) · 140 | 1.000 | 8.750 | 104.23 |
0.844 inches (21.44 mm). The outside diameter is 10.750 inches (273.05 mm) whatever the schedule, so this wall leaves an inside diameter of 9.062 inches.
9.062 inches (230.17 mm). Inside diameter is outside diameter minus twice the wall: 10.750 - 2 x 0.844 = 9.062 inches.
No. NPS 10 is a trade size, not a measurement. The pipe measures 10.750 inches across the outside and 9.062 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
89.38 pounds per foot plain end (133.01 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
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 5 independent published sources:
Sources disagree here. Published tables split on the last digit here - 0.844 in (b3610m-etb), 0.844 in (b3610m-fbc), 0.843 in (b3610m-wikipedia); 21.44 mm (b3610m-ferrobend), 21.44 mm (b3610m-wermac), 21.41 mm (b3610m-wikipedia). The figure printed is 0.844 in (21.44 mm), carried by the majority of the sources. The two readings describe the same wall: they differ by less than a thousandth of an inch, far inside the mill tolerance of minus 12.5 percent on wall thickness.
Last-digit inch walls across the whole table: 0.594, 0.688, 0.719, 0.844, 0.938, 1.094, 1.219, 1.438, 1.969, 2.344 in (b3610m-fbc) against 0.593, 0.687, 0.718, 0.843, 0.937, 1.093, 1.218, 1.437, 1.968, 2.343 in (b3610m-wikipedia). Two families of inch figures are in circulation, one a thousandth of an inch below the other, and they come from rounding the millimetre wall the standard tabulates rather than from any difference in the pipe. The higher family is what the majority of the sources read here carry and is what this site prints; the affected rows say so individually. Nothing turns on the choice: the wall tolerance is minus 12.5 percent, which at a half-inch wall is sixty times the gap.
NPS 14 extra strong (XS): 0.469 in (b3610m-fbc) against 0.500 in (b3610m-etb) against 0.500 in (b3610m-wikipedia). 0.500 in is printed here. Two of the three inch sources give it, both millimetre sources give 12.70 mm which is 0.500 in, and extra strong is a 0.500 in wall at every size from NPS 12 up. The 0.469 in reading looks like a misplaced row in that one chart, but it is recorded rather than deleted.
Nearby sizes