1 inch pipe dimensions: OD and wall thickness by schedule
Deskely Completions team Singapore
A 1 inch pipe, NPS 1 or DN 25, has an outside diameter of 33.4 mm (1.315 inches) in every schedule. The nominal size is a name, not a measurement: the outside diameter is larger than 1 inch. The schedule sets the wall thickness, and with it the inside diameter and the weight.
The table gives every schedule listed for NPS 1 in ASME B36.10M and B36.19M, in mm and inches.
- Outside diameter: 33.4 mm (1.315 in), the same for every schedule.
- Schedule 40: 3.38 mm wall, 26.6 mm inside diameter.
- Schedule 80: 4.55 mm wall, 24.3 mm inside diameter.
- Metric equivalent: DN 25.
1 inch pipe dimensions by schedule
| Schedule | Wall mm (in) | ID mm (in) | kg/m (lb/ft) |
|---|---|---|---|
| Schedule 5S | 1.65 (0.065) | 30.10 (1.185) | 1.29 (0.87) |
| Schedule 10S | 2.77 (0.109) | 27.86 (1.097) | 2.09 (1.41) |
| Schedule 10 | 2.77 (0.109) | 27.86 (1.097) | 2.09 (1.41) |
| Schedule 30 | 2.90 (0.114) | 27.60 (1.087) | 2.18 (1.47) |
| STD (standard) | 3.38 (0.133) | 26.64 (1.049) | 2.50 (1.68) |
| Schedule 40 | 3.38 (0.133) | 26.64 (1.049) | 2.50 (1.68) |
| XS (extra strong) | 4.55 (0.179) | 24.30 (0.957) | 3.24 (2.18) |
| Schedule 80 | 4.55 (0.179) | 24.30 (0.957) | 3.24 (2.18) |
| Schedule 160 | 6.35 (0.250) | 20.70 (0.815) | 4.24 (2.85) |
| XXS (double extra strong) | 9.09 (0.358) | 15.22 (0.599) | 5.45 (3.66) |
Nominal dimensions. Weights are for plain-end carbon steel; stainless steel is about 2 percent heavier. Mill tolerances apply, and your project pipe specification takes precedence.
1 inch pipe outside diameter
The outside diameter of NPS 1 pipe is 33.4 mm, or 1.315 inches, whatever the schedule, so 1 inch fittings and flanges fit every wall thickness. In metric drawings and specifications the same size is called DN 25.
It is larger than 1 inch because, below NPS 14, the nominal size is a traditional name that once roughly matched the bore, not the outside.
Nearby sizes
- 3/4 inch pipe dimensions: OD 26.7 mm
- 1-1/4 inch pipe dimensions: OD 42.2 mm
Every size and schedule in one table: the pipe schedule chart.
The Deskely products for this
Frequently asked questions
What is the OD of 1 inch pipe?
33.4 mm (1.315 inches), the same for every schedule.
What is the wall thickness of 1 inch schedule 40 pipe?
3.38 mm (0.133 in), giving an inside diameter of 26.6 mm (1.049 in).
What is the wall thickness of 1 inch schedule 80 pipe?
4.55 mm (0.179 in), giving an inside diameter of 24.3 mm (0.957 in).
What is 1 inch pipe in DN?
DN 25.
How much does 1 inch schedule 40 pipe weigh?
2.50 kg/m (1.68 lb/ft) for plain-end carbon steel.
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