NPS 20 (DN 500) Pipe — Dimensions, Schedules & Weight
Welded and seamless steel pipe per ASME B36.10M / EN 10220
NPS 20 (DN 500) pipe always has an outside diameter of 508 mm (20") — the schedule changes only the wall, from 6.35 mm at Sch 10 to 50.01 mm at Sch 160. That is the whole logic of the schedule system: OD stays constant so fittings and threads always match, while a higher schedule buys pressure capacity with a thicker wall and a smaller bore.
The most-quoted variant, Sch 20 / STD, has a 9.53 mm wall, a 488.9 mm inside diameter, and weighs 117.15 kg/m — a 6 m length is 702.9 kg. All weights below are plain-end masses from the standard formula (OD − t) × t × 0.02466.
NPS 20 (DN 500) — all schedules
| Schedule | t (mm) | t (in) | ID (mm) | kg/m | lb/ft |
|---|---|---|---|---|---|
| Sch 10 | 6.35 | 0.25 | 495.3 | 78.55 | 52.79 |
| Sch 20 / STD | 9.53 | 0.375 | 488.9 | 117.15 | 78.72 |
| Sch 30 / XS | 12.7 | 0.5 | 482.6 | 155.12 | 104.24 |
| Sch 40 | 15.09 | 0.594 | 477.8 | 183.42 | 123.25 |
| Sch 60 | 20.62 | 0.812 | 466.8 | 247.83 | 166.53 |
| Sch 80 | 26.19 | 1.031 | 455.6 | 311.17 | 209.1 |
| Sch 100 | 32.54 | 1.281 | 442.9 | 381.53 | 256.37 |
| Sch 120 | 38.1 | 1.5 | 431.8 | 441.49 | 296.67 |
| Sch 140 | 44.45 | 1.75 | 419.1 | 508.11 | 341.44 |
| Sch 160 | 50.01 | 1.969 | 408 | 564.81 | 379.54 |
Frequently Asked Questions
What is the outside diameter of 20" pipe?
508 mm (20 inches) — for every schedule. NPS is a nominal name, not a measurement. From NPS 14 up, OD equals the NPS in inches.
What is the wall thickness and ID of 20" Sch 20 / STD?
Sch 20 / STD has a 9.53 mm (0.375") wall, which leaves an inside diameter of 488.9 mm. The table above lists the wall and bore for every schedule of this size.
How much does 20" Sch 20 / STD pipe weigh?
117.15 kg/m (78.72 lb/ft). A 6 m length weighs 702.9 kg, a 12 m length 1,405.7 kg. The heaviest listed schedule, Sch 160, weighs 564.81 kg/m.
What is the difference between STD and Schedule 40?
Up to NPS 10 they are the same wall. From NPS 12 upward they split: STD stays at 9.53 mm (3/8") for all larger sizes, while Sch 40 keeps growing with the diameter. The same happens to XS and Sch 80 above NPS 8.
Values are entered from the governing standard’s published tables and cross-checked programmatically against its mass and section formulas before publication. Spotted an error? Write to advertising@metalabout.net — verified corrections ship within days. About