ASME B36.10M (welded and seamless wrought steel pipe) · DN 125
Outside diameter 5.563" (141.30 mm), wall 0.375" (9.53 mm), inside diameter 4.813" (122.24 mm), 20.80 lb per foot.
| Trade size | NPS 5 · DN 125 |
|---|---|
| Schedule | Schedule 80 · same wall as XS, 80S |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 5.563" · 141.30 mm |
| Wall thickness | 0.375" · 9.53 mm |
| Inside diameter | 4.813" · 122.24 mm |
| Weight, plain end | 20.80 lb/ft · 30.97 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 20.78 lb/ft here, 0.1% from the published 20.80 lb/ft. The published figure is the one printed above.
NPS 5 schedule 80 pipe measures 5.563 in (141.30 mm) across the outside with a 0.375 in wall, so the bore is 4.813 in (122.24 mm). That bore gives a flow area of 18.19 in² and holds 0.9451 US gallons per foot (11.74 litres per metre). The outside diameter is 14.8 times the wall, and the steel itself has a cross-section of 6.112 in² and weighs 20.80 lb per foot plain end. One trade size up, NPS 6 in the same schedule carries 1.43 times the flow area.
Schedule 40 is the next lighter wall at NPS 5: 0.258 in, 0.117 in thinner, which opens the bore to 5.047 in and adds 10.0% to the flow area, for 30% less weight per foot.
Schedule 120 is the next heavier wall at NPS 5: 0.500 in, 0.125 in thicker, which narrows the bore to 4.563 in and cuts 10% from the flow area, for 30% more weight per foot.
Next trade size up in this schedule: NPS 6 schedule 80, bore 5.761 in.
| Flow area | 18.19 in² |
|---|---|
| Capacity | 0.9451 US gal/ft · 11.74 L/m |
| Metal area | 6.112 in² |
| Moment of inertia | 20.67 in⁴ |
| Section modulus | 7.431 in³ |
| Radius of gyration | 1.839 in |
| Outside surface | 1.456 ft² per foot |
Plain geometry of a hollow circle with OD = 5.563 in and ID = 4.813 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 5 pipe has an outside diameter of 5.563 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 80 the wall is 0.375 inches, so the bore comes out at 4.813 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 5.563 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.109 | 5.345 | 6.36 |
| Schedule 10 · 10S | 0.134 | 5.295 | 7.78 |
| Schedule 40 · STD, 40S | 0.258 | 5.047 | 14.63 |
| Schedule 120 | 0.500 | 4.563 | 27.06 |
| Schedule 160 | 0.625 | 4.313 | 32.99 |
| Double extra strong (XXS) | 0.750 | 4.063 | 38.59 |
0.375 inches (9.53 mm). The outside diameter is 5.563 inches (141.30 mm) whatever the schedule, so this wall leaves an inside diameter of 4.813 inches.
4.813 inches (122.24 mm). Inside diameter is outside diameter minus twice the wall: 5.563 - 2 x 0.375 = 4.813 inches.
No. NPS 5 is a trade size, not a measurement. The pipe measures 5.563 inches across the outside and 4.813 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
20.80 pounds per foot plain end (30.97 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
Yes, at NPS 5. XS and 80S are the same 0.375 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:
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