Millimeters to Inches
Convert millimeters to inches instantly. 1 mm = 0.0393700787 in. Includes the exact factor, a conversion table of common values and the definition of both units.
How to convert millimeters to inches
To convert millimeters to inches, divide by 25.4 (multiply by 0.0393700787). The relationship is fixed, so the same factor works for any quantity — there is nothing to look up and nothing that changes with temperature, location or context.
in = mm × 0.0393700787
Millimeters to Inches conversion table
The values people look up most often, rounded for reading. Use the calculator above for anything in between.
| Millimeters | Inches |
|---|---|
| 1 mm | 0.03937 in |
| 2 mm | 0.07874 in |
| 3 mm | 0.11811 in |
| 5 mm | 0.19685 in |
| 10 mm | 0.393701 in |
| 20 mm | 0.787402 in |
| 25 mm | 0.984252 in |
| 50 mm | 1.968504 in |
| 100 mm | 3.937008 in |
| 500 mm | 19.685039 in |
| 1,000 mm | 39.370079 in |
What is a millimeter?
A thousandth of a metre. The default fine unit on metric engineering drawings.
What is a inch?
Exactly 25.4 mm since the 1959 international yard and pound agreement.
The formula
in = mm × 0.0393700787
Every result on this page comes from this formula. Nothing is rounded until the final display, so figures match a spreadsheet to the cent.
How to use the Millimeters to Inches
- Type the number of millimeters you want to convert.
- Read the result in inches straight away — there is no button to press.
- Check the table below for the values that come up most often, or reverse the conversion with the linked inches to millimeters page.
Millimeters to Inches — frequently asked questions
How many inches are in a millimeter?
One millimeter equals 0.0393700787 in. in = mm × 0.0393700787
What is the formula to convert millimeters to inches?
The formula is in = mm × 0.0393700787. It is an exact definition rather than an approximation, so the conversion never drifts no matter how large the number.
How do I convert inches back to millimeters?
Divide instead of multiplying: one inch is 25.4 mm. The reverse converter is linked in the related tools list.
Is this conversion exact?
Yes. Both units are defined against the same base unit by international agreement, so the factor is exact — any rounding you see is only in the display, which you can widen by entering more decimal places.
Is this millimeters to inches free to use?
Yes. Every calculator on the site is free, needs no sign-up, and runs entirely in your browser, so your figures never leave your device.
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About this calculator
Written and reviewed by The Samsung Calculator editorial team. Every calculator is written against a published formula, reviewed against at least one independent reference implementation, and dated when it changes.
Last reviewed August 15, 2026 · Calculation runs client-side · No data collected · Report an error