Nominal pipe size to outside diameter in mm
Type a value in NPS to get it in mm OD instantly.
33.4mm OD
That's about the same as a 1" gas line.
Convert the other way: mm OD to NPS
What it means
How big is that pipe?
Steel pipe to ASME B36.10 / ISO 6708. The outside diameter is the same for every schedule; the wall, and so the bore, changes. Copper tube and PVC have their own sizes.
The math
How to convert NPS to mm OD
Pipe sizes are a table: NPS 2 = DN 50 = 60.3 mm (2.375 in) OD, NPS 4 = DN 100 = 114.3 mm. From NPS 14 the OD equals the NPS in inches.
Example: 1 NPS = 33.401 mm OD.
Every unit
That pipe in every system
Tables
NPS to mm OD conversion table
| NPS | mm OD |
|---|---|
| 1/8 NPS | 10.287 mm OD |
| 1/4 NPS | 13.716 mm OD |
| 3/8 NPS | 17.145 mm OD |
| 1/2 NPS | 21.336 mm OD |
| 3/4 NPS | 26.67 mm OD |
| 1 NPS | 33.401 mm OD |
| 1 1/4 NPS | 42.164 mm OD |
| 1 1/2 NPS | 48.26 mm OD |
| 2 NPS | 60.325 mm OD |
| 2 1/2 NPS | 73.025 mm OD |
| 3 NPS | 88.9 mm OD |
| 4 NPS | 114.3 mm OD |
| 5 NPS | 141.3 mm OD |
| 6 NPS | 168.275 mm OD |
| 8 NPS | 219.075 mm OD |
| 10 NPS | 273.05 mm OD |
| 12 NPS | 323.85 mm OD |
| 14 NPS | 355.6 mm OD |
| 16 NPS | 406.4 mm OD |
| 18 NPS | 457.2 mm OD |
| 20 NPS | 508 mm OD |
| 24 NPS | 609.6 mm OD |
mm OD to NPS conversion table
| mm OD | NPS |
|---|---|
| 10.3 mm OD | ≈1/8 NPS |
| 13.7 mm OD | ≈1/4 NPS |
| 17.1 mm OD | ≈3/8 NPS |
| 21.3 mm OD | ≈1/2 NPS |
| 26.7 mm OD | ≈3/4 NPS |
| 33.4 mm OD | ≈1 NPS |
| 42.2 mm OD | ≈1 1/4 NPS |
| 48.3 mm OD | ≈1 1/2 NPS |
| 60.3 mm OD | ≈2 NPS |
| 73 mm OD | ≈2 1/2 NPS |
| 88.9 mm OD | 3 NPS |
| 114 mm OD | ≈4 NPS |
| 141 mm OD | ≈5 NPS |
| 168 mm OD | ≈6 NPS |
| 219 mm OD | ≈8 NPS |
| 273 mm OD | ≈10 NPS |
| 324 mm OD | ≈12 NPS |
| 356 mm OD | ≈14 NPS |
| 406 mm OD | ≈16 NPS |
| 457 mm OD | ≈18 NPS |
| 508 mm OD | 20 NPS |
Quick answers
Quick answers
- How many mm OD is 1 NPS?
- 1 NPS is 33.401 mm OD.
- How many mm OD is 10 NPS?
- 10 NPS is 273.05 mm OD.
The units
About these units
Nominal pipe size (NPS)
The US nominal size in inches: ½, 1, 2…
Outside diameter in mm (mm OD)
The actual outside diameter in millimeters.
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