Millimeters to Inches

1 mm = 0.03937008 in

Millimeters to inches is needed when metric parts, rainfall totals, or product specs must be explained to people used to inches. US hobbyists buying metric hardware, photographers comparing sensor or lens measurements, and gardeners reading rainfall reports all run into it. Each millimeter is exactly 1/25.4 of an inch.

From

When you need to convert millimeters to inches

Understanding rainfall or snowfall totals reported in millimeters
Finding the closest inch-sized wrench or drill bit for a metric part
Comparing smartphone thickness or jewelry dimensions given in millimeters
Reading tire widths, which are listed in millimeters on the sidewall

How to convert millimeters to inches

in = mm × 0.03937008

Equivalently: in = mm ÷ 25.4.

Example: 5 mm = 0.1968504 in

Common lengths in millimeters

Millimeters (mm)	Inches (in)
1 mm	0.03937008 in
3 mm	0.1181102 in
5 mm	0.1968504 in
6 mm	0.2362205 in
8 mm	0.3149606 in
10 mm	0.3937008 in
12 mm	0.4724409 in
20 mm	0.7874016 in
25 mm	0.984252 in
50 mm	1.968504 in

Tips for converting millimeters to inches

Divide millimeters by 25 for a quick estimate. It runs about 1.6% high, which is fine for rough comparisons.
Metric and fractional-inch sizes rarely line up exactly, so check the converted value before substituting a metric part for an inch-sized one.
For precise work, keep the result in decimal inches rather than rounding to the nearest fraction.

Millimeters to Inches conversion table

Millimeters (mm)	Inches (in)
1 mm	0.03937008 in
2 mm	0.07874016 in
3 mm	0.1181102 in
4 mm	0.1574803 in
5 mm	0.1968504 in
6 mm	0.2362205 in
7 mm	0.2755906 in
8 mm	0.3149606 in
9 mm	0.3543307 in
10 mm	0.3937008 in
15 mm	0.5905512 in
20 mm	0.7874016 in
25 mm	0.984252 in
30 mm	1.181102 in
40 mm	1.574803 in
50 mm	1.968504 in
75 mm	2.952756 in
100 mm	3.937008 in
250 mm	9.84252 in
500 mm	19.68504 in
1,000 mm	39.37008 in

About the units

Millimeters: The millimeter is a metric unit of length equal to one thousandth of a meter, used for precise measurements in engineering, manufacturing and rainfall.

Inches: The inch is an imperial and US customary unit of length, defined since 1959 as exactly 2.54 centimeters. It is used for screen sizes, clothing and hardware in the US and UK.

Frequently asked questions

How many inches are in 1 millimeter?

1 millimeter equals 0.03937008 inches.

How many millimeters are in 1 inch?

1 inch equals 25.4 millimeters.

How do I convert millimeters to inches?

Use the formula in = mm × 0.03937008. Equivalently, in = mm ÷ 25.4.

What is 10 millimeters in inches?

10 millimeters equals 0.3937008 inches.

Related conversions

Factors: NIST SP 811 · SI Brochure · NIST Handbook 44 — Updated October 17, 2026