Inches to Millimeters Converter
1 inch is equal to 25.4 millimeters, or 2.54 cm.
Enter a value in the converter to get the result. This page explains the formula, works through examples and lists common values in a conversion table.
How to convert inches to millimeters
Multiply the value in inches by 25.4 to get millimeters.
mm = × 25.4- 1Start with the value in inches: 1 in.
- 2Apply the formula: × 25.4 = 25.4.
- 3Round to the precision you need: 25.4 mm.
For a quick estimate without a calculator, multiply by 25. For 1 in that gives about 25 mm.
Examples
Inches to Millimeters conversion table
1 inch in other units
The same value in every other unit of this category. Each row links to the full conversion.
| Unit | Formula | 1 in equals |
|---|---|---|
| Inches to Millimeters | mm = × 25.4 | 25.4 mm |
| Inches to Centimeters | cm = × 2.54 | 2.54 cm |
| Inches to Meters | m = × 0.0254 | 0.0254 m |
| Inches to Kilometers | km = × 0.0000254 | 0.0000254 km |
| Inches to Yards | yd = ÷ 36 | 0.0277778 yd |
| Inches to US Survey Feet | ft-us = ÷ 12.000024 | 0.0833332 ft-us |
| Inches to Feet | ft = ÷ 12 | 0.0833333 ft |
| Inches to Miles | mi = ÷ 63,360 | 0.0000157828 mi |
Millimeters to Inches
The reverse conversion uses the inverse formula. For example, 1 mm is 0.0393701 in. Use the millimeters to inches converter for other values.
in = ÷ 25.4About the units
Inch (in)
A unit of length in the imperial and US customary systems. 1 in = 25.4 mm.
Millimeter (mm)
A unit of length in the metric system. 1 mm = 0.0393701 in.
Accuracy and rounding
The calculation uses exact decimal arithmetic, so the conversion itself adds no error. Results are rounded to six significant figures; the formula steps show more digits.
More inches to millimeters conversions
FAQ
How many millimeters are in one inch?
One inch is equal to 25.4 millimeters.
How do I convert millimeters back to inches?
Use the formula in = ÷ 25.4. See the millimeters to inches converter.