NPS 1/4 (DN 8) Pipe — Dimensions, Schedules & Weight
Welded and seamless steel pipe per ASME B36.10M / EN 10220
NPS 1/4 (DN 8) pipe always has an outside diameter of 13.7 mm (0.539") — the schedule changes only the wall, from 2.24 mm at Sch 40 / STD to 3.02 mm at Sch 80 / XS. 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 40 / STD, has a 2.24 mm wall, a 9.2 mm inside diameter, and weighs 0.63 kg/m — a 6 m length is 3.8 kg. All weights below are plain-end masses from the standard formula (OD − t) × t × 0.02466.
NPS 1/4 (DN 8) pipe, Sch 40 / STD: cross-section drawn to scale (OD 13.7 mm, wall 2.24 mm, ID 9.2 mm)NPS 1/4 (DN 8) — all schedules
| Schedule | t (mm) | t (in) | ID (mm) | kg/m | lb/ft |
|---|
| Sch 40 / STD | 2.24 | 0.088 | 9.2 | 0.63 | 0.43 |
| Sch 80 / XS | 3.02 | 0.119 | 7.7 | 0.8 | 0.53 |
Frequently Asked Questions
What is the outside diameter of 1/4" pipe?
13.7 mm (0.539 inches) — for every schedule. NPS is a nominal name, not a measurement; the actual OD of NPS 1/4 is larger than 1/4 inches for historical reasons. From NPS 14 up, OD equals the NPS in inches.
What is the wall thickness and ID of 1/4" Sch 40 / STD?
Sch 40 / STD has a 2.24 mm (0.088") wall, which leaves an inside diameter of 9.2 mm. The table above lists the wall and bore for every schedule of this size.
How much does 1/4" Sch 40 / STD pipe weigh?
0.63 kg/m (0.43 lb/ft). A 6 m length weighs 3.8 kg, a 12 m length 7.6 kg. The heaviest listed schedule, Sch 80 / XS, weighs 0.8 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