mm to inches

Convert millimeters to inches — or inches to millimeters — with common inch fractions.

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How to use mm to inches

1Type a length in millimeters to see it in inches.
2Or type in the inches box to convert inches to mm.
3Copy the result with one click.
4Use the charts for common sizes and inch fractions.

Millimeters and inches

Engineering drawings, 3D printing, jewelry, screws and drill bits, camera sensors and electronics use millimeters, while many tools, lumber and hardware in the US are sized in inches and fractions of an inch. This converter turns millimeters into inches and inches into millimeters as you type.

Inch fractions in millimeters

Fraction	Decimal inch	Millimeters
1/32	0.03125	0.79
1/16	0.0625	1.59
1/8	0.125	3.18
3/16	0.1875	4.76
1/4	0.25	6.35
3/8	0.375	9.53
1/2	0.5	12.70
5/8	0.625	15.88
3/4	0.75	19.05
1	1	25.40

Common metric sizes

Item	Millimeters	Inches
Credit card thickness	0.76	0.03
Pencil diameter	7	0.28
M8 bolt	8	0.31
3.5 mm audio jack	3.5	0.14
35 mm film width	35	1.38
100 mm	100	3.94

Related tools

Convert larger lengths with cm to inches and feet to meters, or switch to micrometers, yards and more with the Unit Converter.

Frequently asked questions

How many millimeters are in an inch?

Exactly 25.4 mm. This has been the international definition of the inch since 1959.

How do I convert mm to inches?

Divide by 25.4. For 10 mm: 10 ÷ 25.4 = 0.394 in. To convert inches to millimeters, multiply by 25.4.

How do I convert decimal inches to a fraction?

Multiply the decimal part by 16 (or 32 or 64) and round to get sixteenths. 0.394 in × 16 = 6.3, so 10 mm is about 6/16 = 3/8 inch. The chart below lists common fractions.

Why do drill bits and wrenches come in both sizes?

Metric (mm) and imperial (inch) tools are used side by side, especially in the US. A 13 mm wrench is very close to 1/2 inch (12.7 mm), but not identical — using the wrong one can round off bolt heads.

What is a "thou" or mil?

A thou (or mil) is a thousandth of an inch, equal to 0.0254 mm. It's used for sheet thickness, coatings and machining tolerances.

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