Schedule 40 pipe dimensions
Standard-weight (Schedule 40) carbon steel pipe dimensions per ASME B36.10, from 1/8 to 12 inch nominal size. Nominal pipe size (NPS) is a label, not a measurement: the outside diameter is fixed for a given NPS while the wall thickness sets the inside diameter.
Schedule 40 steel pipe
| NPS | OD (in) | Wall (in) | ID (in) | Weight (lb/ft) |
|---|---|---|---|---|
| 1/8 | 0.405 | 0.068 | 0.269 | 0.24 |
| 1/4 | 0.540 | 0.088 | 0.364 | 0.42 |
| 3/8 | 0.675 | 0.091 | 0.493 | 0.57 |
| 1/2 | 0.840 | 0.109 | 0.622 | 0.85 |
| 3/4 | 1.050 | 0.113 | 0.824 | 1.13 |
| 1 | 1.315 | 0.133 | 1.049 | 1.68 |
| 1-1/4 | 1.660 | 0.140 | 1.380 | 2.27 |
| 1-1/2 | 1.900 | 0.145 | 1.610 | 2.72 |
| 2 | 2.375 | 0.154 | 2.067 | 3.65 |
| 2-1/2 | 2.875 | 0.203 | 2.469 | 5.79 |
| 3 | 3.500 | 0.216 | 3.068 | 7.58 |
| 4 | 4.500 | 0.237 | 4.026 | 10.79 |
| 5 | 5.563 | 0.258 | 5.047 | 14.62 |
| 6 | 6.625 | 0.280 | 6.065 | 18.97 |
| 8 | 8.625 | 0.322 | 7.981 | 28.55 |
| 10 | 10.750 | 0.365 | 10.020 | 40.48 |
| 12 | 12.750 | 0.406 | 11.938 | 53.52 |
Outside diameter stays the same across schedules for a given NPS; only the wall thickness changes, so a heavier schedule has a smaller bore. Weights are for plain carbon steel and are nominal. For 14 inch and larger, NPS equals the actual outside diameter.
Need the flow area or volume?
Use the inside diameter here with the engineering calculators to find flow area, velocity, or pipe volume.
How pipe schedules work
A schedule number sets the wall thickness of a pipe for each nominal size: higher schedule, thicker wall, higher pressure rating. Schedule 40 is the standard weight used for most general plumbing and low-pressure work. Because the outside diameter is fixed, a thicker wall eats into the bore, so Schedule 80 of the same NPS flows less than Schedule 40.
NPS is not the bore
Nominal pipe size loosely matches the old inside diameter of Schedule 40 pipe in small sizes, but it is really just a label. A 1 inch NPS Schedule 40 pipe has a 1.315 inch outside diameter and a 1.049 inch bore. Always use the listed inside diameter, not the NPS, for flow calculations.
FAQ
What is the inside diameter of 2 inch Schedule 40 pipe?
About 2.067 inches, with a 2.375 inch outside diameter and a 0.154 inch wall.
Does Schedule 40 pipe have the same outside diameter as Schedule 80?
Yes. For a given nominal size the outside diameter is identical; Schedule 80 just has a thicker wall and a smaller bore.
What does NPS mean?
Nominal pipe size, a label for pipe diameter. It sets the outside diameter for each size but is not the actual bore, which depends on the schedule.