Convert Millimeters to Inches
1 millimeter is 0.04 in. One millimeter is exactly 0.0393700787402 inches.
One millimeter is 0.039370079 inches. To convert millimeters to inches, multiply by 0.039370079; to go the other way, divide by 0.039370079 or multiply by 25.4. The relation is exact but the figure is not: it is a rounding of a number that does not terminate, and it follows from NIST. One thousandth of a meter.
Factor checked against the defining standard · How we check
- Millimeters × 0.039370079
1 * 0.03937010.039 in
1 millimeter in every length unit
| Unit | Value | Exact factor |
|---|---|---|
| inches | 0.03937007874 in | × 0.0393700787402 |
| feet | 0.003280839895 ft | × 0.00328083989501 |
| yards | 0.001093613298 yd | × 0.00109361329834 |
| miles | 0.0000006213711922 mi | × 0.000000621371192237 |
| millimeters (as entered) | 1 mm | — |
| decimetres | 0.01 dm | × 0.01 |
| centimeters | 0.1 cm | × 0.1 |
| meters | 0.001 m | × 0.001 |
| kilometers | 0.000001 km | × 0.000001 |
| nautical miles | 0.0000005399568035 nmi | × 0.000000539956803456 |
| micrometers | 1,000 µm | × 1,000 |
| nanometers | 1,000,000 nm | × 1,000,000 |
| thou | 39.37007874 thou | × 39.3700787402 |
Factors are entered by hand from NIST rather than derived from a units library, so the ones that terminate are exact rather than rounded.
The same converter answers this pair however it is written: millimetres to inches is the British spelling of the same units — the metre and the litre are spelled that way outside the United States and the quantity does not change.
How do you convert millimeters to inches? The converter and the working
- 1.Take the measurement in millimeters.
- 2.Multiply by 0.039370079 — that is how many inches fit in one millimeter.
- 3.To go back the other way, divide by 0.039370079, or multiply by 25.4.
Worked example: 25 millimeters to inches
- Formula
- mm × 0.039370079 = in
- Arithmetic
- 25 × 0.039370079 = 0.98 in
- Answer
- 25 mm = 0.98 in
The factor is rounded for display; the figure above is computed from the full value.
Millimeters to inches conversion table
| Millimeters | Inches |
|---|---|
| 1 mm | 0.04 in |
| 2 mm | 0.08 in |
| 3 mm | 0.12 in |
| 4 mm | 0.16 in |
| 5 mm | 0.2 in |
| 6 mm | 0.24 in |
| 7 mm | 0.28 in |
| 8 mm | 0.31 in |
| 9 mm | 0.35 in |
| 10 mm | 0.39 in |
| 12 mm | 0.47 in |
| 15 mm | 0.59 in |
| 20 mm | 0.79 in |
| 25 mm | 0.98 in |
| 50 mm | 1.97 in |
| 100 mm | 3.94 in |
| 200 mm | 7.87 in |
| 300 mm | 11.81 in |
| 500 mm | 19.69 in |
| 1000 mm | 39.37 in |
| 2000 mm | 78.74 in |
| 5000 mm | 196.85 in |
| 10000 mm | 393.7 in |
What is a millimeter?
One thousandth of a meter. The working unit of metric engineering drawings, which avoid decimals by using it throughout.
What is an inch?
Exactly 25.4 millimeters since the 1959 international yard and pound agreement, and one twelfth of a foot.
How many inches are in a millimeter?
One millimeter is 0.039370079 inches. Going the other way, one inch is 25.4 millimeters. Both figures come from the same defined relation rather than from a measurement, which is why they are the same today as they were in 1959.
Every length unit here
The whole group — 13 units with their symbols and the size of each one in meters — is on the conversion index, along with every pair it makes. The table above already gives each of them relative to a millimeter.
Source: NIST — international yard and pound agreement (inch = 25.4 mm exactly)
Cite this page
- APA
- Rule Calculator. (2026). Convert Millimeters to inches. Rule Calculator. https://rulecalculators.com/convert/millimeter-to-inch
- MLA
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- Chicago
- Rule Calculator. "Convert Millimeters to inches." Rule Calculator. Last reviewed August 16, 2026. https://rulecalculators.com/convert/millimeter-to-inch.
The date is when the figures on this page were last checked against their source, not the day you opened it. Add your own access date if your style needs one.
Questions people actually ask
- How many inches are in a millimeter?
- 0.039370079. Exactly 25.4 millimeters since the 1959 international yard and pound agreement, and one twelfth of a foot.
- How do I convert inches back to millimeters?
- Divide by 0.039370079, or multiply by 25.4 — they are the same operation.
Other length conversions
Inches to millimeters — the same conversion the other way.