1-1/4 inch pipe dimensions: OD and wall thickness by schedule
Deskely Completions team Singapore
A 1-1/4 inch pipe, NPS 1-1/4 or DN 32, has an outside diameter of 42.2 mm (1.660 inches) in every schedule. The nominal size is a name, not a measurement: the outside diameter is larger than 1-1/4 inch. The schedule sets the wall thickness, and with it the inside diameter and the weight.
The table gives every schedule listed for NPS 1-1/4 in ASME B36.10M and B36.19M, in mm and inches.
- Outside diameter: 42.2 mm (1.660 in), the same for every schedule.
- Schedule 40: 3.56 mm wall, 35.1 mm inside diameter.
- Schedule 80: 4.85 mm wall, 32.5 mm inside diameter.
- Metric equivalent: DN 32.
1-1/4 inch pipe dimensions by schedule
| Schedule | Wall mm (in) | ID mm (in) | kg/m (lb/ft) |
|---|---|---|---|
| Schedule 5S | 1.65 (0.065) | 38.90 (1.531) | 1.65 (1.11) |
| Schedule 10S | 2.77 (0.109) | 36.66 (1.443) | 2.69 (1.81) |
| Schedule 10 | 2.77 (0.109) | 36.66 (1.443) | 2.69 (1.81) |
| Schedule 30 | 2.97 (0.117) | 36.26 (1.428) | 2.87 (1.93) |
| STD (standard) | 3.56 (0.140) | 35.08 (1.381) | 3.39 (2.28) |
| Schedule 40 | 3.56 (0.140) | 35.08 (1.381) | 3.39 (2.28) |
| XS (extra strong) | 4.85 (0.191) | 32.50 (1.280) | 4.47 (3.00) |
| Schedule 80 | 4.85 (0.191) | 32.50 (1.280) | 4.47 (3.00) |
| Schedule 160 | 6.35 (0.250) | 29.50 (1.161) | 5.61 (3.77) |
| XXS (double extra strong) | 9.70 (0.382) | 22.80 (0.898) | 7.77 (5.22) |
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.
1-1/4 inch pipe outside diameter
The outside diameter of NPS 1-1/4 pipe is 42.2 mm, or 1.660 inches, whatever the schedule, so 1-1/4 inch fittings and flanges fit every wall thickness. In metric drawings and specifications the same size is called DN 32.
It is larger than 1-1/4 inch because, below NPS 14, the nominal size is a traditional name that once roughly matched the bore, not the outside.
Nearby sizes
- 1 inch pipe dimensions: OD 33.4 mm
- 1-1/2 inch pipe dimensions: OD 48.3 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 1-1/4 inch pipe?
42.2 mm (1.660 inches), the same for every schedule.
What is the wall thickness of 1-1/4 inch schedule 40 pipe?
3.56 mm (0.140 in), giving an inside diameter of 35.1 mm (1.381 in).
What is the wall thickness of 1-1/4 inch schedule 80 pipe?
4.85 mm (0.191 in), giving an inside diameter of 32.5 mm (1.280 in).
What is 1-1/4 inch pipe in DN?
DN 32.
How much does 1-1/4 inch schedule 40 pipe weigh?
3.39 kg/m (2.28 lb/ft) for plain-end carbon steel.
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