MM to Inches Converter

Convert millimeters to inches by dividing by 25.4. Enter a size in mm to get decimal inches and the nearest fraction. Example: 25 mm = 0.9843 in.

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Millimeters (mm)

Decimal places

How to use the MM to Inches Converter

Type the value in millimeters.
Choose how many decimal places you want.
Press Calculate to see the value in inches, with the formula and steps.

Formula and method

inches = millimeters ÷ 25.4

An inch is exactly 25.4 mm. Machinists and woodworkers often want the nearest fraction, so this calculator returns it to 1/64 inch. For example, 10 mm = 0.3937 in, which is about 25/64 in.

mm to in conversion chart

Millimeters	Inches	Nearest 1/64 in
1 mm	0.0394 in	3/64 in
2 mm	0.0787 in	5/64 in
3 mm	0.1181 in	1/8 in
4 mm	0.1575 in	5/32 in
5 mm	0.1969 in	13/64 in
6 mm	0.2362 in	15/64 in
8 mm	0.315 in	5/16 in
10 mm	0.3937 in	25/64 in
12 mm	0.4724 in	15/32 in
15 mm	0.5906 in	19/32 in
16 mm	0.6299 in	5/8 in
19 mm	0.748 in	3/4 in
20 mm	0.7874 in	25/32 in
25 mm	0.9843 in	63/64 in
30 mm	1.1811 in	1 3/16 in
40 mm	1.5748 in	1 37/64 in
50 mm	1.9685 in	1 31/32 in
100 mm	3.937 in	3 15/16 in

Fastener and drill sizes

Metric hardware is sized in mm while US tools use fractions. An M6 bolt is 6 mm (0.236 in, close to 1/4 in), a 10 mm socket is 0.394 in (about 25/64), and 19 mm is 0.748 in (about 3/4). A 12 mm drill bit is 0.472 in, just under 15/32 in.

Camera and small parts

Lens sizes, film and thread diameters are in mm. A 35 mm film frame is 1.378 in wide, a 50 mm lens has a 1.969 in focal length, and a 3 mm hex key is 0.118 in. Tolerances are usually given in mm, so keep four decimal places when machining.

What are millimeters and inches?

A millimeter is one thousandth of a meter, or one tenth of a centimeter. It is the standard unit for small parts, fasteners and lens sizes.

An inch is one twelfth of a foot. Since the international agreement of 1959 it is defined as exactly 2.54 centimeters.

How to convert millimeters to inches step by step

Write the value you want to convert: 14 mm.
Apply the rule millimeters to inches: ÷ 25.4.
Calculate: 14 ÷ 25.4 = 0.5512 in.
Check a second value, 63 mm: 63 ÷ 25.4 = 2.4803 in.

Round the answer to the precision you need. For quick checks use the mental estimate in the formula section above, and use the converter for exact results.

Full mm to in chart

mm	in	mm	in	mm	in
5 mm	0.1969 in	55 mm	2.1654 in	105 mm	4.1339 in
10 mm	0.3937 in	60 mm	2.3622 in	110 mm	4.3307 in
15 mm	0.5906 in	65 mm	2.5591 in	115 mm	4.5276 in
20 mm	0.7874 in	70 mm	2.7559 in	120 mm	4.7244 in
25 mm	0.9843 in	75 mm	2.9528 in	125 mm	4.9213 in
30 mm	1.1811 in	80 mm	3.1496 in	130 mm	5.1181 in
35 mm	1.378 in	85 mm	3.3465 in	135 mm	5.315 in
40 mm	1.5748 in	90 mm	3.5433 in	140 mm	5.5118 in
45 mm	1.7717 in	95 mm	3.7402 in	145 mm	5.7087 in
50 mm	1.9685 in	100 mm	3.937 in	150 mm	5.9055 in

Frequently asked questions

How many mm are in an inch?

Exactly 25.4 mm.

How do I convert 10 mm to inches?

10 / 25.4 = 0.3937 inches.

Is 1 mm the same as 1/16 inch?

No. 1/16 inch is 1.5875 mm, so 1 mm is about 0.63 of 1/16 inch.

Sources

NIST: Unit conversion factors

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