ASME B36.10M (welded and seamless wrought steel pipe) · DN 25
Outside diameter 1.315" (33.40 mm), wall 0.133" (3.38 mm), inside diameter 1.049" (26.64 mm), 1.68 lb per foot.
| Trade size | NPS 1 · DN 25 |
|---|---|
| Schedule | Schedule 40 · also STD |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 1.315" · 33.40 mm |
| Wall thickness | 0.133" · 3.38 mm |
| Inside diameter | 1.049" · 26.64 mm |
| Weight, plain end | 1.68 lb/ft · 2.5 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 1.68 lb/ft here, 0.1% from the published 1.68 lb/ft. The published figure is the one printed above.
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 schedule 40 the wall is 0.133 inches, so the bore comes out at 1.049 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 | 0.065 | 1.185 | 0.87 |
| Schedule 10 | 0.109 | 1.097 | 1.41 |
| Schedule 30 | 0.114 | 1.087 | 1.46 |
| Schedule 80 | 0.179 | 0.957 | 2.17 |
| Schedule 160 | 0.250 | 0.815 | 2.85 |
| Standard wall (STD) | 0.133 | 1.049 | 1.68 |
| Extra strong (XS) | 0.179 | 0.957 | 2.17 |
| Double extra strong (XXS) | 0.358 | 0.599 | 3.66 |
| Schedule 5S | 0.065 | 1.185 | not published |
| Schedule 10S | 0.109 | 1.097 | not published |
| Schedule 40S | 0.133 | 1.049 | not published |
| Schedule 80S | 0.179 | 0.957 | not published |
0.133 inches (3.38 mm). The outside diameter is 1.315 inches (33.40 mm) whatever the schedule, so this wall leaves an inside diameter of 1.049 inches.
1.049 inches (26.64 mm). Inside diameter is outside diameter minus twice the wall: 1.315 - 2 x 0.133 = 1.049 inches.
No. NPS 1 is a trade size, not a measurement. The pipe measures 1.315 inches across the outside and 1.049 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
1.68 pounds per foot plain end (2.5 kg per metre), for carbon steel. Stainless of the same dimensions runs a little lighter, and the figure excludes coatings, linings and fittings.
Yes, at NPS 1. STD is the same 0.133 inch wall here. That coincidence is per size and does not hold everywhere: standard wall and schedule 40 part company above NPS 10, and extra strong and schedule 80 part company above NPS 8.
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