Dimensions
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 94.62 lb/ft here, 0.1% from the published 94.71 lb/ft. The published figure is the one printed above.
NPS 24 standard wall (std) in numbers
NPS 24 standard wall (std) pipe measures 24.000 in (609.60 mm) across the outside with a 0.375 in wall, so the bore is 23.250 in (590.54 mm). That bore gives a flow area of 424.6 in² and holds 22.05 US gallons per foot (273.9 litres per metre). The outside diameter is 64.0 times the wall, and the steel itself has a cross-section of 27.83 in² and weighs 94.71 lb per foot plain end.
Schedule 10 is the next lighter wall at NPS 24: 0.250 in, 0.125 in thinner, which opens the bore to 23.500 in and adds 2.2% to the flow area, for 33% less weight per foot.
Extra strong (XS) is the next heavier wall at NPS 24: 0.500 in, 0.125 in thicker, which narrows the bore to 23.000 in and cuts 2.1% from the flow area, for 33% more weight per foot.
Worked out from the dimensions
Plain geometry of a hollow circle with OD = 24.000 in and ID = 23.250 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.
Why 24 inch pipe is not 24 inches
Nominal Pipe Size is a label, not a measurement. NPS 24 pipe has an outside diameter of 24.000 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at standard wall (std) the wall is 0.375 inches, so the bore comes out at 23.250 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.
Other schedules in NPS 24
Same outside diameter of 24.000 inches throughout - only the wall and the bore move.
Frequently asked questions
What is the wall thickness of 24 inch standard wall (std) pipe?
0.375 inches (9.53 mm). The outside diameter is 24.000 inches (609.60 mm) whatever the schedule, so this wall leaves an inside diameter of 23.250 inches.
What is the inside diameter of 24 inch standard wall (std) pipe?
23.250 inches (590.54 mm). Inside diameter is outside diameter minus twice the wall: 24.000 - 2 x 0.375 = 23.250 inches.
Is 24 inch pipe actually 24 inches?
No. NPS 24 is a trade size, not a measurement. The pipe measures 24.000 inches across the outside and 23.250 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
How much does 24 inch standard wall (std) pipe weigh?
94.71 pounds per foot plain end (141.12 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
Is standard wall (std) the same as 20 or 40S at this size?
Yes, at NPS 24. 20 and 40S 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.
Where this table stops
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.
Where these figures come from
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: