Length
Convert inch (in) to millimetre (mm). Length units span pipe diameters (mm, inch), plant dimensions (m, ft), and roughness (µm) — mixing metric and imperial is routine.
1 in = 25.4 mm
To convert inch to millimetre, multiply the in value by 25.4. To go the other way, divide by 25.4 (or multiply by 0.03937008).
| in | mm |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 5 | 127 |
| 10 | 254 |
| 25 | 635 |
| 50 | 1270 |
| 100 | 2540 |
| 250 | 6350 |
| 500 | 12700 |
| 1000 | 25400 |
Pipe sizes are labelled in inches (NPS) but calculated in mm; equipment layouts mix metres and feet.
Velocity scales with the inverse square of diameter, so a small length error compounds quickly in flow calculations.
Worked example. A length of 3.937008 in is 100 mm.
Multiply the value in in by 25.4 to get mm. For example, 10 in = 254 mm.
1 in equals 25.4 mm.
Pipe sizes are labelled in inches (NPS) but calculated in mm; equipment layouts mix metres and feet.