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Inches to Millimeters

Convert inches (in) to millimeters (mm) — instant and accurate

1 in = 25.4 mm  ·  To convert inches to millimeters, multiply by 25.4.

25.4 mm

Inches to Millimeters Conversion Table

InchesMillimeters
1 in25.4 mm
2 in50.8 mm
3 in76.2 mm
4 in101.6 mm
5 in127 mm
6 in152.4 mm
7 in177.8 mm
8 in203.2 mm
9 in228.6 mm
10 in254 mm
15 in381 mm
20 in508 mm
25 in635 mm
30 in762 mm
40 in1016 mm
50 in1270 mm
75 in1905 mm
100 in2540 mm
250 in6350 mm
500 in12700 mm
1000 in25400 mm

Formula

millimeters = inches × 25.4
inches = millimeters × 0.039370079
Example: 5 in × 25.4 = 127 mm

About the Inches-to-Millimeters Conversion

Converting inches to millimetres is essential in precision engineering, machining, watchmaking, firearms specifications, and screen pixel-pitch calculations. The factor is exact: 1 inch = 25.4 mm by international definition.

Real-World Examples

  • 1 in (one inch) = 25.4 mm
  • 12 in (one foot) = 304.8 mm
  • 15.6 in (laptop screen) = 396.24 mm
  • 0.5 in (half-inch) = 12.7 mm

Millimeters to Inches (Reverse)

MillimetersInches
1 mm0.0393701 in
2 mm0.0787402 in
3 mm0.11811 in
4 mm0.15748 in
5 mm0.19685 in
6 mm0.23622 in
7 mm0.275591 in
8 mm0.314961 in
9 mm0.354331 in
10 mm0.393701 in
15 mm0.590551 in
20 mm0.787402 in
25 mm0.984252 in
30 mm1.1811 in
40 mm1.5748 in
50 mm1.9685 in
75 mm2.95276 in
100 mm3.93701 in
250 mm9.84252 in
500 mm19.685 in
1000 mm39.3701 in

Frequently Asked Questions

How many millimeters are in a inch?

1 inch equals 25.4 millimeters.

How do I convert inches to millimeters?

Multiply the value in inches by 25.4 to get millimeters. For example, 5 in × 25.4 = 127 mm.

How do I convert millimeters back to inches?

Multiply the value in millimeters by 0.039370079 to get inches. Equivalently, divide by 25.4.

How many inches are in a millimeter?

1 millimeter equals 0.039370079 inches.

How many millimeters is 1 in?

1 in (one inch) equals 25.4 mm.

Is the inches-to-millimeters conversion exact?

Yes. 1 in = 25.4 mm is an exact value defined by international agreement.

About Inches and Millimeters

The inch (symbol in) is an imperial and US customary unit defined as exactly 25.4 millimetres since the 1959 international agreement.

The millimetre (symbol mm) equals one thousandth of a metre and is the standard unit for precision engineering and small-scale specifications.

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