Inches to Millimeters Converter in → mm

1 inch (in) = 25.4 millimeters (mm). Type a value below — the conversion happens instantly, entirely on your device.

From

1 in = 25.4 mm

Precision

1 inches = 25.4 millimeters

1 × 25.4 = 25.4

1 in equals 25.4 mm, so multiplying by 25.4 converts the value. The result describes the exact same quantity — only the measuring stick changes.

Rate this tool:

Anonymous — no tracking

How to convert inches to millimeters

millimeters = inches × 25.4 — multiply the inch value by 25.4.

Example: 10 in = 254 mm.

To convert the other way: inches = millimeters ÷ 25.4 — or use the dedicated mm to in converter .

Inches to Millimeters conversion table

Inches (in)	Millimeters (mm)
0.1	2.54
0.25	6.35
0.5	12.7
1	25.4
2	50.8
3	76.2
4	101.6
5	127
6	152.4
7	177.8
8	203.2
9	228.6
10	254
15	381
20	508
25	635
30	762
40	1016
50	1270
75	1905
100	2540
250	6350
500	12,700
1000	25,400

About the units

What is a inch?

An inch (in) is an imperial and US customary unit defined as exactly 25.4 millimeters since 1959. Twelve inches make one foot; screens, wheels and paper sizes are commonly measured in inches.

What is a millimeter?

A millimeter (mm) is one thousandth of a meter, the SI base unit of length. It is commonly used for small measurements such as paper thickness, screw sizes and rainfall.

Frequently asked questions

How many millimeters are in 1 inch?

1 inch (in) = 25.4 millimeters (mm).

What is the formula to convert inches to millimeters?

millimeters = inches × 25.4 — multiply the inch value by 25.4.

How do I convert in to mm without a calculator?

Multiply by 25.4 for a close estimate. Exact factor: 1 in = 25.4 mm.

Is this in-to-mm converter accurate and private?

Yes. It uses the exact internationally defined conversion factors and computes results locally in your browser — your input is never sent to a server, and the page keeps working offline.