mm to inches

Millimeters to Inches: in = mm ÷ 25.4. Type a number and read the answer straight off the scale.

Millimeters

Inches

10 mm is 0.393701 in.

mm to inches chart of common values

Millimeters to Inches chart
Millimeters	Inches
1 mm	0.039 in
2 mm	0.079 in
3 mm	0.118 in
4 mm	0.157 in
5 mm	0.197 in
6 mm	0.236 in
8 mm	0.315 in
10 mm	0.394 in
12 mm	0.472 in
13 mm	0.512 in
15 mm	0.591 in
16 mm	0.63 in
19 mm	0.748 in
20 mm	0.787 in
22 mm	0.866 in
25 mm	0.984 in
30 mm	1.181 in
35 mm	1.378 in
40 mm	1.575 in
45 mm	1.772 in
50 mm	1.969 in
60 mm	2.362 in
70 mm	2.756 in
75 mm	2.953 in
80 mm	3.15 in
90 mm	3.543 in
100 mm	3.937 in
150 mm	5.906 in
200 mm	7.874 in
250 mm	9.843 in
300 mm	11.811 in

How to convert millimeters to inches

The formula

in = mm ÷ 25.4. Dividing by 25.4 is the same as multiplying by 0.03937008.

Worked through for 10

Divide 10 by 25.4. The result is 0.393701 in to six places. Rounded, that is 0.394 in.

In your head

Divide by 25, then trim a little: 50 mm → 2 in (exactly 1.969 in).

More mm to inches

The other way: inches to mm.

Questions

What is the formula for mm to inches?

in = mm ÷ 25.4. One millimeter is 0.03937 inches.

How can I estimate it in my head?

Divide by 25, then trim a little: 50 mm → 2 in (exactly 1.969 in).

Where do the conversion factors come from?

The pound and the inch were defined in metric units by the 1959 international yard and pound agreement: one pound is exactly 0.45359237 kg and one inch is exactly 2.54 cm.