ASME B36.10M (welded and seamless wrought steel pipe) · DN 500
Outside diameter 20.000" (508.00 mm), wall 0.812" (20.62 mm), inside diameter 18.376" (466.76 mm), 166.56 lb per foot.
| Trade size | NPS 20 · DN 500 |
|---|---|
| Schedule | Schedule 60 |
| Standard | ASME B36.10M (welded and seamless wrought steel pipe) |
| Outside diameter | 20.000" · 508.00 mm |
| Wall thickness | 0.812" · 20.62 mm |
| Inside diameter | 18.376" · 466.76 mm |
| Weight, plain end | 166.56 lb/ft · 247.84 kg/m |
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 166.40 lb/ft here, 0.1% from the published 166.56 lb/ft. The published figure is the one printed above.
NPS 20 schedule 60 pipe measures 20.000 in (508.00 mm) across the outside with a 0.812 in wall, so the bore is 18.376 in (466.76 mm). That bore gives a flow area of 265.2 in² and holds 13.78 US gallons per foot (171.1 litres per metre). The outside diameter is 24.6 times the wall, and the steel itself has a cross-section of 48.95 in² and weighs 166.56 lb per foot plain end. One trade size up, NPS 22 in the same schedule carries 1.21 times the flow area.
Schedule 40 is the next lighter wall at NPS 20: 0.594 in, 0.218 in thinner, which opens the bore to 18.812 in and adds 4.8% to the flow area, for 26% less weight per foot.
Schedule 80 is the next heavier wall at NPS 20: 1.031 in, 0.219 in thicker, which narrows the bore to 17.938 in and cuts 4.7% from the flow area, for 26% more weight per foot.
Next trade size up in this schedule: NPS 22 schedule 60, bore 20.250 in.
| Flow area | 265.2 in² |
|---|---|
| Capacity | 13.78 US gal/ft · 171.1 L/m |
| Metal area | 48.95 in² |
| Moment of inertia | 2257 in⁴ |
| Section modulus | 225.7 in³ |
| Radius of gyration | 6.790 in |
| Outside surface | 5.236 ft² per foot |
Plain geometry of a hollow circle with OD = 20.000 in and ID = 18.376 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 20 pipe has an outside diameter of 20.000 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at schedule 60 the wall is 0.812 inches, so the bore comes out at 18.376 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 20.000 inches throughout - only the wall and the bore move.
| Schedule | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|
| Schedule 5 · 5S | 0.188 | 19.624 | 39.82 |
| Schedule 10 | 0.250 | 19.500 | 52.70 |
| Schedule 40 | 0.594 | 18.812 | 123.23 |
| Schedule 80 | 1.031 | 17.938 | 209.06 |
| Schedule 100 | 1.281 | 17.438 | 256.34 |
| Schedule 120 | 1.500 | 17.000 | 296.65 |
| Schedule 140 | 1.750 | 16.500 | 341.41 |
| Schedule 160 | 1.969 | 16.062 | 379.53 |
| Standard wall (STD) · 20, 40S | 0.375 | 19.250 | 78.67 |
| Extra strong (XS) · 30, 80S | 0.500 | 19.000 | 104.23 |
| Schedule 10S | 0.218 | 19.564 | not published |
0.812 inches (20.62 mm). The outside diameter is 20.000 inches (508.00 mm) whatever the schedule, so this wall leaves an inside diameter of 18.376 inches.
18.376 inches (466.76 mm). Inside diameter is outside diameter minus twice the wall: 20.000 - 2 x 0.812 = 18.376 inches.
No. NPS 20 is a trade size, not a measurement. The pipe measures 20.000 inches across the outside and 18.376 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
166.56 pounds per foot plain end (247.84 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 4 independent published sources:
Nearby sizes