Length
Convert millimetre (mm) to thousandth of an inch (mil). Length units span pipe diameters (mm, inch), plant dimensions (m, ft), and roughness (µm) — mixing metric and imperial is routine.
1 mm = 39.37008 mil
To convert millimetre to thousandth of an inch, multiply the mm value by 39.37008. To go the other way, divide by 39.37008 (or multiply by 0.0254).
| mm | mil |
|---|---|
| 1 | 39.37008 |
| 2 | 78.74016 |
| 5 | 196.8504 |
| 10 | 393.7008 |
| 25 | 984.252 |
| 50 | 1968.504 |
| 100 | 3937.008 |
| 250 | 9842.52 |
| 500 | 19685.04 |
| 1000 | 39370.08 |
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 100 mm is 3937.008 mil.
Multiply the value in mm by 39.37008 to get mil. For example, 10 mm = 393.7008 mil.
1 mm equals 39.37008 mil.
Pipe sizes are labelled in inches (NPS) but calculated in mm; equipment layouts mix metres and feet.