Dimensions
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 429.39 lb/ft here, 0.1% from the published 429.79 lb/ft. The published figure is the one printed above.
NPS 24 schedule 120 in numbers
NPS 24 schedule 120 pipe measures 24.000 in (609.60 mm) across the outside with a 1.812 in wall, so the bore is 20.376 in (517.56 mm). That bore gives a flow area of 326.1 in² and holds 16.94 US gallons per foot (210.4 litres per metre). The outside diameter is 13.2 times the wall, and the steel itself has a cross-section of 126.3 in² and weighs 429.79 lb per foot plain end.
Schedule 100 is the next lighter wall at NPS 24: 1.531 in, 0.281 in thinner, which opens the bore to 20.938 in and adds 5.6% to the flow area, for 14% less weight per foot.
Schedule 140 is the next heavier wall at NPS 24: 2.062 in, 0.250 in thicker, which narrows the bore to 19.876 in and cuts 4.8% from the flow area, for 13% more weight per foot.
Worked out from the dimensions
Plain geometry of a hollow circle with OD = 24.000 in and ID = 20.376 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.
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 schedule 120 the wall is 1.812 inches, so the bore comes out at 20.376 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.
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 schedule 120 pipe?
1.812 inches (46.02 mm). The outside diameter is 24.000 inches (609.60 mm) whatever the schedule, so this wall leaves an inside diameter of 20.376 inches.
What is the inside diameter of 24 inch schedule 120 pipe?
20.376 inches (517.56 mm). Inside diameter is outside diameter minus twice the wall: 24.000 - 2 x 1.812 = 20.376 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 20.376 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
How much does 24 inch schedule 120 pipe weigh?
429.79 pounds per foot plain end (640.07 kg per metre), for carbon steel. The figure excludes coatings, linings and fittings.
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: