Inches to Millimetres
Type a value in Inches and get the result in Millimetres, calculated exactly.
30 Inches = 762 Millimetres
Precision
Exact factorThis result is exact.
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Formula
mm = in × 25.4
To convert Inches to Millimetres, multiply the value by 25.4.
Worked examples
- 1 in × 25.4 = 25.4 mm
- 30 in × 25.4 = 762 mm
- 100 in × 25.4 = 2,540 mm
This factor is exact by definition.
Conversion table
| Inches (in) | Millimetres (mm) |
|---|---|
| 1 | 25.4 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 5 | 127 |
| 6 | 152.4 |
| 7 | 177.8 |
| 8 | 203.2 |
| 9 | 228.6 |
| 10 | 254 |
| 15 | 381 |
| 20 | 508 |
| 25 | 635 |
| 30 | 762 |
| 40 | 1,016 |
| 50 | 1,270 |
| 60 | 1,524 |
| 70 | 1,778 |
| 75 | 1,905 |
| 80 | 2,032 |
| 90 | 2,286 |
| 100 | 2,540 |
Values marked ≈ are rounded; the rest are exact.
Reverse table: Millimetres to Inches
| Millimetres (mm) | Inches (in) |
|---|---|
| 1 | ≈ 0.03937008 |
| 2 | ≈ 0.07874016 |
| 3 | ≈ 0.1181102 |
| 4 | ≈ 0.1574803 |
| 5 | ≈ 0.1968504 |
| 6 | ≈ 0.2362205 |
| 7 | ≈ 0.2755906 |
| 8 | ≈ 0.3149606 |
| 9 | ≈ 0.3543307 |
| 10 | ≈ 0.3937008 |
| 15 | ≈ 0.5905512 |
| 20 | ≈ 0.7874016 |
| 25 | ≈ 0.984252 |
| 30 | ≈ 1.181102 |
| 40 | ≈ 1.574803 |
| 50 | ≈ 1.968504 |
| 60 | ≈ 2.362205 |
| 70 | ≈ 2.755906 |
| 75 | ≈ 2.952756 |
| 80 | ≈ 3.149606 |
| 90 | ≈ 3.543307 |
| 100 | ≈ 3.937008 |
Unit definitions
- Inches in
- Exactly 0.0254 metres, by the 1959 international agreement.
- Millimetres mm
- One thousandth of a metre.
Questions people ask
Inches to Millimetres: what is the conversion factor?
One in is 25.4 mm.
How do I convert Inches to Millimetres?
Use the formula above. For example, 30 in = 762 mm.
Is the conversion exact?
Yes. Both units have exact definitions, so the factor is exact; a result is only rounded when its decimals never end.
Factors checked 19 October 2026.