Pipe schedules · NPS 2-1/2
ASME B36.10M (welded and seamless wrought steel pipe) · DN 65
2-1/2 inch Double extra strong pipe
Outside diameter 2.875" (73.02 mm), wall 0.552" (14.02 mm), inside diameter 1.771" (44.98 mm), 13.71 lb per foot.
Dimensions
Cross-check: the standard plain-end weight formula W = 10.6802 x t x (OD - t) gives 13.70 lb/ft here, 0.1% from the published 13.71 lb/ft. The published figure is the one printed above.
Why 2-1/2 inch pipe is not 2-1/2 inches
Nominal Pipe Size is a label, not a measurement. NPS 2-1/2 pipe has an outside diameter of 2.875 inches, and it keeps that outside diameter in every schedule made. What the schedule number changes is the wall: at double extra strong (xxs) the wall is 0.552 inches, so the bore comes out at 1.771 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 2-1/2
Same outside diameter of 2.875 inches throughout - only the wall and the bore move.
Frequently asked questions
What is the wall thickness of 2-1/2 inch double extra strong (xxs) pipe?
0.552 inches (14.02 mm). The outside diameter is 2.875 inches (73.02 mm) whatever the schedule, so this wall leaves an inside diameter of 1.771 inches.
What is the inside diameter of 2-1/2 inch double extra strong (xxs) pipe?
1.771 inches (44.98 mm). Inside diameter is outside diameter minus twice the wall: 2.875 - 2 x 0.552 = 1.771 inches.
Is 2-1/2 inch pipe actually 2-1/2 inches?
No. NPS 2-1/2 is a trade size, not a measurement. The pipe measures 2.875 inches across the outside and 1.771 inches across the bore in this schedule. Only the outside diameter is fixed across schedules.
How much does 2-1/2 inch double extra strong (xxs) pipe weigh?
13.71 pounds per foot plain end (20.39 kg per metre), for carbon steel. Stainless of the same dimensions runs a little lighter, and the figure excludes coatings, linings and fittings.
Not published here
One schedule at NPS 2-1/2 appears in only one of the published tables cross-checked for this section, so it is named rather than printed: 120. Everything shown above carries at least two independent sources.
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 5 independent published sources:
Nearby sizes
Double extra strong (XXS) in other trade sizes