Millimeters to Inches Converter

Millimeters back to inches lets you read metric engineering specs through an imperial lens. It is the conversion of choice for US machinists, mechanics, and hobbyists when working with imported parts, metric fasteners, or product dimensions published only in millimeters.

Millimeters (mm)

Inches (in)

Decimal places:

Looking for the reverse? Inches to Millimeters converter →

How to Convert Millimeters to Inches

To convert millimeters to inches, multiply the number of millimeters by 0.0393701.

Formula: in = mm × 0.0393701

Worked Examples

1 millimeter = 1 × 0.03937 = 0.03937 in
5 millimeters = 5 × 0.03937 = 0.19685 in
12 millimeters = 12 × 0.03937 = 0.472441 in
36 millimeters = 36 × 0.03937 = 1.417323 in

Why Convert Millimeters to Inches?

Looking up the inch equivalent of a metric drill bit, tap, or end mill
Reading watch lug, bracelet, or strap widths published in millimeters when shopping a US-market product
Translating millimeter-spec ammunition calibers (9 mm, 7.62 mm) to inch equivalents for cross-reference
Sizing imported screws, bolts, and threaded inserts against an inch-based fastener inventory

Millimeters to Inches Conversion Table

Millimeters (mm)	Inches (in)
0.01 mm	0.000394 in
0.1 mm	0.003937 in
0.25 mm	0.009843 in
0.5 mm	0.019685 in
0.75 mm	0.029528 in
1 mm	0.03937 in
1.5 mm	0.059055 in
2 mm	0.07874 in
2.5 mm	0.098425 in
3 mm	0.11811 in
4 mm	0.15748 in
5 mm	0.19685 in
6 mm	0.23622 in
7 mm	0.275591 in
8 mm	0.314961 in
9 mm	0.354331 in
10 mm	0.393701 in
11 mm	0.433071 in
12 mm	0.472441 in
13 mm	0.511811 in
14 mm	0.551181 in
15 mm	0.590551 in
16 mm	0.629921 in
17 mm	0.669291 in
18 mm	0.708661 in
19 mm	0.748031 in
20 mm	0.787402 in
24 mm	0.944882 in
30 mm	1.181102 in
36 mm	1.417323 in
48 mm	1.889764 in
60 mm	2.362205 in
72 mm	2.834646 in
84 mm	3.307087 in
96 mm	3.779528 in
100 mm	3.937008 in
120 mm	4.724409 in
144 mm	5.669291 in
200 mm	7.874016 in
300 mm	11.811024 in
500 mm	19.685039 in
1000 mm	39.370079 in

What Is a Millimeter?

A millimeter is a metric unit of length equal to one thousandth (1/1000) of a meter. It is the smallest commonly used metric unit for length.

The millimeter shares its origin with the meter, dating to the 1790s French definition of the metric system. As precision manufacturing matured in the 19th and 20th centuries, the millimeter became the preferred unit for engineering drawings outside the United States — fine enough for tight tolerances, but still readable without specialised tooling.

In everyday use: Millimeters dominate mechanical engineering, machining, and CAD drawings, as well as ammunition calibers (9 mm) and the thickness of materials like glass, sheet metal, or smartphone bezels. Camera lens focal lengths, watch case diameters, and most consumer-electronics dimensions are also published in millimeters.

The millimeter symbol is mm.

What Is an Inch?

An inch is a unit of length equal to exactly 25.4 millimeters, defined in 1959 as part of the international yard and pound agreement.

The inch traces back to early English measurement, originally tied to the width of a human thumb or three barleycorns laid end-to-end. After centuries of regional variation, the international inch was standardized in 1959 by an agreement among English-speaking countries to exactly 25.4 millimeters, replacing the slightly different US survey inch for most purposes.

In everyday use: Inches are the standard unit for screen sizes (a 15-inch laptop), TV diagonals, paper formats in the US, plumbing pipe diameters, and clothing dimensions like waistlines and shoe insoles. They remain dominant in US construction, woodworking, and any industry that grew around imperial drawings.

The inch symbol is in.

Precision and Accuracy

1 mm = 0.0393701 in (the exact reciprocal of 25.4). The factor itself is exact; the trailing digits beyond six decimals repeat and are usually rounded for display.

For most everyday purposes — recipes, room sizing, shopping — four decimal places of precision are more than enough. Engineering and scientific work may require additional digits or scientific notation for very small or very large results.

Common Millimeters to Inches Conversions

1 millimeters to in 2 millimeters to in 5 millimeters to in 10 millimeters to in 15 millimeters to in 20 millimeters to in 25 millimeters to in 30 millimeters to in 40 millimeters to in 50 millimeters to in 60 millimeters to in 70 millimeters to in 80 millimeters to in 90 millimeters to in 100 millimeters to in

References

National Institute of Standards and Technology (NIST) — SI Units: Length
International Bureau of Weights and Measures (BIPM) — The International System of Units (SI)