Inches to millimetres
Convert inches to millimetres. To convert inches to millimetres, multiply by 25.4.
Factors from their legal definitions.
Show the workings
| Step | Sum | Answer |
|---|---|---|
| One inch in metres | 0.9144 m ÷ 36 | 0.025 m |
| One millimetre in metres | a thousandth of a metre | 0.001 m |
| 1 inch in metres | 1 × 0.0254 | 0.025 m |
| In millimetres | 0.0254 ÷ 0.001 | 25.4 mm |
Where the figures come from
- A yard in metres: 0.914 m per yard. Source: Weights and Measures Act 1985, Schedule 1. Checked 13 November 2026.
- Inches in a yard: 36 inches per yard. Source: Weights and Measures Act 1985, Schedule 1. Checked 13 November 2026.
Inches to millimetres table
| Inches | Millimetres |
|---|---|
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127 mm |
| 6 in | 152.4 mm |
| 7 in | 177.8 mm |
| 8 in | 203.2 mm |
| 9 in | 228.6 mm |
| 10 in | 254 mm |
| 12 in | 304.8 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 30 in | 762 mm |
| 40 in | 1,016 mm |
| 50 in | 1,270 mm |
| 75 in | 1,905 mm |
| 100 in | 2,540 mm |
How to convert inches to millimetres
One inch is 25.4 millimetres, and one millimetre is 0.03937 inches. So to turn inches into millimetres, multiply by 25.4. For example, 1 inches × 25.4 = 25.4 millimetres.
Where the numbers come from
Imperial units are defined in law as exact amounts of metric ones. These are the definitions this converter uses:
- A yard in metres: 0.914 m per yard. Source: Weights and Measures Act 1985, Schedule 1.
- Inches in a yard: 36 inches per yard. Source: Weights and Measures Act 1985, Schedule 1.
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