ASME B36.10M (welded and seamless wrought steel pipe) · DN 25
Outside diameter 1.315" (33.40 mm), wall 0.358" (9.09 mm), inside diameter 0.599" (15.22 mm), 3.66 lb per foot.
| Trade size | NPS 1 · DN 25 |
|---|---|
| Schedule | Double extra strong (XXS) |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 1.315" · 33.40 mm |
| Wall thickness | 0.358" · 9.09 mm |
| Inside diameter | 0.599" · 15.22 mm |
| Weight, plain end | 3.66 lb/ft · 5.45 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 3.66 lb/ft here, 0.0% from the published 3.66 lb/ft. The published figure is the one printed above.
NPS 1 double extra strong (xxs) pipe measures 1.315 in (33.40 mm) across the outside with a 0.358 in wall, so the bore is 0.599 in (15.22 mm). That bore gives a flow area of 0.2818 in² and holds 0.01464 US gallons per foot (0.1818 litres per metre). The outside diameter is 3.7 times the wall, and the steel itself has a cross-section of 1.076 in² and weighs 3.66 lb per foot plain end. One trade size up, NPS 1-1/4 in the same schedule carries 2.24 times the flow area.
Schedule 160 is the next lighter wall at NPS 1: 0.250 in, 0.108 in thinner, which opens the bore to 0.815 in and adds 85% to the flow area, for 22% less weight per foot.
Next trade size up in this schedule: NPS 1-1/4 double extra strong (xxs), bore 0.896 in.
| Flow area | 0.2818 in² |
|---|---|
| Capacity | 0.01464 US gal/ft · 0.1818 L/m |
| Metal area | 1.076 in² |
| Moment of inertia | 0.1405 in⁴ |
| Section modulus | 0.2136 in³ |
| Radius of gyration | 0.3613 in |
| Outside surface | 0.3443 ft² per foot |
Plain geometry of a hollow circle with OD = 1.315 in and ID = 0.599 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 pipe has an outside diameter of 1.315 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at double extra strong (xxs) the wall is 0.358 inches, so the bore comes out at 0.599 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 1.315 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.065 | 1.185 | 0.87 |
| Schedule 10 · 10S | 0.109 | 1.097 | 1.41 |
| Schedule 30 | 0.114 | 1.087 | 1.46 |
| Schedule 40 · STD, 40S | 0.133 | 1.049 | 1.68 |
| Schedule 80 · XS, 80S | 0.179 | 0.957 | 2.17 |
| Schedule 160 | 0.250 | 0.815 | 2.85 |
0.358 inches (9.09 mm). The outside diameter is 1.315 inches (33.40 mm) whatever the schedule, so this wall leaves an inside diameter of 0.599 inches.
0.599 inches (15.22 mm). Inside diameter is outside diameter minus twice the wall: 1.315 - 2 x 0.358 = 0.599 inches.
No. NPS 1 is a trade size, not a measurement. The pipe measures 1.315 inches across the outside and 0.599 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
3.66 pounds per foot plain end (5.45 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:
Nearby sizes