Millimetres to inches

Convert millimetres to inches. To convert millimetres to inches, divide by 25.4.

Factors from their legal definitions.

100 millimetres is 3.937 inches.

One millimetre	0.03937 in
One inch	25.4 mm

Show the workings

Step	Sum	Answer
One millimetre in metres	a thousandth of a metre	0.001 m
One inch in metres	0.9144 m ÷ 36	0.025 m
100 millimetres in metres	100 × 0.001	0.1 m
In inches	0.1 ÷ 0.0254	3.937 in

Where the figures come from

A yard in metres: 0.914 m per yard. Source: Weights and Measures Act 1985, Schedule 1. Checked 13 November 2026.
Inches in a yard: 36 inches per yard. Source: Weights and Measures Act 1985, Schedule 1. Checked 13 November 2026.

Millimetres to inches table

Millimetres	Inches
0.5 mm	0.01969 in
1 mm	0.03937 in
2 mm	0.07874 in
3 mm	0.1181 in
4 mm	0.1575 in
5 mm	0.1969 in
6 mm	0.2362 in
7 mm	0.2756 in
8 mm	0.315 in
9 mm	0.3543 in
10 mm	0.3937 in
12 mm	0.4724 in
15 mm	0.5906 in
20 mm	0.7874 in
25 mm	0.9843 in
30 mm	1.181 in
40 mm	1.575 in
50 mm	1.969 in
75 mm	2.953 in
100 mm	3.937 in

How to convert millimetres to inches

One millimetre is 0.03937 inches, and one inch is 25.4 millimetres. So to turn millimetres into inches, divide by 25.4. For example, 100 millimetres ÷ 25.4 = 3.937 inches.

Where the numbers come from

Imperial units are defined in law as exact amounts of metric ones. These are the definitions this converter uses:

A yard in metres: 0.914 m per yard. Source: Weights and Measures Act 1985, Schedule 1.
Inches in a yard: 36 inches per yard. Source: Weights and Measures Act 1985, Schedule 1.

More converters

Work out something else

Inches to millimetres
Convert inches to mm, with the sum shown.
Centimetres to inches
Convert cm to inches, with the sum shown.
Inches to centimetres
Convert inches to cm, with the sum shown.