Length

mil to µm conversion

Convert thousandth of an inch (mil) to micrometre (µm). Length units span pipe diameters (mm, inch), plant dimensions (m, ft), and roughness (µm) — mixing metric and imperial is routine.

1 mil = 25.4 µm

Formula

To convert thousandth of an inch to micrometre, multiply the mil value by 25.4. To go the other way, divide by 25.4 (or multiply by 0.03937008).

mil to µm conversion table

mil	µm
1	25.4
2	50.8
5	127
10	254
25	635
50	1270
100	2540
250	6350
500	12700
1000	25400

Used in practice

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 3937.008 mil is 100000 µm.

Frequently asked questions

How do you convert thousandth of an inch to micrometre?

Multiply the value in mil by 25.4 to get µm. For example, 10 mil = 254 µm.

What is 1 mil in µm?

1 mil equals 25.4 µm.

Where is this conversion used?