What is Nominal Pipe Sizing
Inch sizes relate to the nominal (approx.) bore of the PIPE and are not literal physical dimensions.
- For instance, 1" Pipe DOES NOT measure 25mm in diameter.
- Therefore a 1" Socket DOES NOT measure 25mm internally.
The below tables provide a dimensional reference for Imperial and Metric pipes, and their acceptable tolerances.
A tolerance is the allowable limit of variation (represented as min and max) of a specific pipe size. For example; a 1" pipe should measure 33.6mm however may measure as low as 33.4mm and as high as 33.7mm.
| Nominal Size | Actual Size | Acceptable Tolerances | |
|---|---|---|---|
| millimeters | min | max | |
| 12 | 12.0 | 12.2 | |
| 16 | 16.0 | 16.2 | |
| 20 | 20.0 | 20.2 | |
| 25 | 25.0 | 25.2 | |
| 32 | 32.0 | 30.2 | |
| 40 | 40.0 | 40.2 | |
| 50 | 50.0 | 50.2 | |
| 63 | 63.0 | 63.2 | |
| 75 | 75.0 | 75.3 | |
| 90 | 90.0 | 90.3 | |
| 110 | 110.0 | 110.4 | |
| 125 | 125.0 | 125.4 | |
| 140 | 140.0 | 140.5 | |
| 160 | 160.0 | 160.5 | |
| 180 | 180.0 | 180.6 | |
| 200 | 200.0 | 200.6 | |
| 225 | 225.0 | 225.7 | |
| 250 | 250.0 | 250.8 | |
| 280 | 280.0 | 280.9 | |
| 315 | 315.0 | 316 | |
| 355 | 355.0 | 356.1 | |
| 400 | 400.0 | 401.2 | |
| 450 | 450.0 | 451.4 | |
| 500 | 500.0 | 501.5 | |
Nominal (Inch) pipe sizes and their respective tolerances
| Nominal Size | Actual Size | Acceptable Tolerances | |
|---|---|---|---|
| inches | millimeters | min | max |
| 3/8" | 17.1 | 17.0 | 17.3 |
| 1/2" | 21.4 | 21.2 | 21.5 |
| 3/4" | 26.7 | 26.6 | 26.9 |
| 1" | 33.6 | 33.4 | 33.7 |
| 1 1/4" | 42.2 | 42.1 | 42.4 |
| 1 1/2" | 48.3 | 48.1 | 48.4 |
| 2" | 60.3 | 60.2 | 60.5 |
| 2 1/2" | 75.2 | 75.0 | 75.3 |
| 3" | 88.9 | 88.7 | 89.1 |
| 4" | 114.3 | 114.1 | 114.5 |
| 5" | 140.2 | 140.0 | 140.5 |
| 6" | 168.3 | 168.0 | 168.5 |
| 8" | 219.1 | 218.8 | 219.4 |
| 10" | 273.0 | 272.6 | 273.4 |
| 12" | 323.9 | 323.4 | 324.3 |
| 14" | 355.6 | 355.0 | 356.1 |
| 16" | 406.4 | 405.9 | 406.9 |
| 18" | 457.2 | 456.7 | 457.7 |
Metric pipe sizes and their respective tolerances