Length converter

Millimeters to Inches

Millimeters and Inches measure the same quantity in different unit systems. The relationship is 1 mm = 0.03937008 in, which gives 0.03937008 in per mm. Below you can convert any value, check a worked example and read the full chart.

Millimeters (mm)

Inches (in)

Formula 1 mm = 0.03937008 in

Need the other direction? Inches to Millimeters.

How to convert Millimeters to Inches

The millimetre is one thousandth of a metre and is the usual unit for engineering tolerances. The inch is defined as exactly 2.54 centimetres, which anchors the whole imperial length system.

To convert Millimeters to Inches, multiply the value in mm by 0.03937008. For example, 10 mm × 0.03937008 = 0.39370079 in. This works because the ratio between the two units is constant for every value in length.

Worked examples

mm	in
1 mm	0.03937008 in
2.5 mm	0.0984252 in
5 mm	0.19685039 in
10 mm	0.39370079 in
25 mm	0.98425197 in
50 mm	1.968504 in
100 mm	3.937008 in

Reverse conversion

in	mm
1 in	25.4 mm
5 in	127 mm
10 in	254 mm
25 in	635 mm
50 in	1,270 mm
100 in	2,540 mm

When this conversion is useful

This is the calculation you need when you are working across metric and imperial measurements, shopping abroad or reading a spec sheet. Because the factor is fixed, you can use the same number for a single measurement or for a batch: 1,000 mm is 39.370079 in.

Is the conversion exact?

Yes for practical use: the factors come from international definitions, with rounding applied only for display.

Reference: BIPM SI Brochure and NIST SP 811. Last reviewed: 2026-11-01.

mm to in conversion chart

The chart lists the most requested values. For a value that is not here, use the converter at the top of the page.

Millimeters (mm)	Inches (in)
1 mm	0.03937008 in
2 mm	0.07874016 in
3 mm	0.11811024 in
4 mm	0.15748031 in
5 mm	0.19685039 in
6 mm	0.23622047 in
7 mm	0.27559055 in
8 mm	0.31496063 in
9 mm	0.35433071 in
10 mm	0.39370079 in
11 mm	0.43307087 in
12 mm	0.47244094 in
13 mm	0.51181102 in
14 mm	0.5511811 in
15 mm	0.59055118 in
16 mm	0.62992126 in
17 mm	0.66929134 in
18 mm	0.70866142 in
19 mm	0.7480315 in
20 mm	0.78740157 in
21 mm	0.82677165 in
22 mm	0.86614173 in
23 mm	0.90551181 in
24 mm	0.94488189 in
25 mm	0.98425197 in
26 mm	1.023622 in
27 mm	1.062992 in
28 mm	1.102362 in
29 mm	1.141732 in
30 mm	1.181102 in
31 mm	1.220472 in
32 mm	1.259843 in
33 mm	1.299213 in
34 mm	1.338583 in
35 mm	1.377953 in
36 mm	1.417323 in
37 mm	1.456693 in
38 mm	1.496063 in
39 mm	1.535433 in
40 mm	1.574803 in
41 mm	1.614173 in
42 mm	1.653543 in
43 mm	1.692913 in
44 mm	1.732283 in
45 mm	1.771654 in
46 mm	1.811024 in
47 mm	1.850394 in
48 mm	1.889764 in
49 mm	1.929134 in
50 mm	1.968504 in
60 mm	2.362205 in
70 mm	2.755906 in
80 mm	3.149606 in
90 mm	3.543307 in
100 mm	3.937008 in

Frequently asked questions

How many Inches are in 1 Millimeters?

1 mm equals 0.03937008 in.

How do I convert Millimeters to Inches?

Multiply the mm value by 0.03937008. Example: 25 mm = 0.98425197 in.

What is 2.5 mm in in?

2.5 mm = 0.0984252 in.

Is the mm to in conversion exact?

Yes for practical use: the factors come from international definitions, with rounding applied only for display.

Does the calculator work offline?

Yes. The conversion runs in your browser with JavaScript, so it works after the page has loaded, even without a connection.

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