Millimetres to Inches Converter
Convert millimetres (mm) to inches (in) instantly. Enter a value in millimetres and this converter returns the equivalent in inches, using the exact factor of 0.039370079. One millimetre is 0.039370079 inches, and one inch is 25.4 millimetres, so you can convert either way. The factor follows the standard definitions of the metre and the international inch, so it is consistent and reliable for school work, trade, engineering, travel and everyday measuring. The formula, a worked example and a quick-reference table are below.
The formula
Multiply millimetres by 0.039370079 to get inches. In symbols, in = mm × 0.039370079. To go the other way, multiply inches by 25.4 to get millimetres.
Worked example
Convert 10 millimetres to inches: 10 × 0.039370079 = 0.393700787 inches.
Quick reference
| Millimetres | Inches |
|---|---|
| 1 mm | 0.039370079 in |
| 2 mm | 0.078740158 in |
| 5 mm | 0.196850394 in |
| 10 mm | 0.393700787 in |
| 25 mm | 0.984251969 in |
| 50 mm | 1.96850394 in |
| 100 mm | 3.93700787 in |
Frequently asked questions
How many inches are in one millimetre?
One millimetre equals 0.039370079 inches. Multiply the number of millimetres by 0.039370079 to convert.
What is the formula to convert millimetres to inches?
Millimetres times 0.039370079 equals inches. To reverse it, multiply inches by 25.4 to get millimetres.
Is the mm to in conversion exact?
The factor comes from the standard definitions of the metre and the international inch (0.0254 m exactly), so the underlying conversion is exact. Displayed results are rounded for readability.
Who this converter is for
This converter is for students, tradespeople, travellers and anyone who needs to change millimetres into inches quickly and accurately.
What this converter assumes
- You enter a length in millimetres.
- The factor used is 0.039370079 inches per millimetre.
- Results are rounded for display.
Sources
Related converters
- Length Converter: convert between any length units.
- Unit Converter: convert many kinds of units.
- Millimetres to Centimetres Converter: convert millimetres to centimetres.
- Millimetres to Metres Converter: convert millimetres to metres.
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