Enter millimetres or centimetres and get inches two ways — the exact decimal and the nearest fraction, the way rulers and tape measures actually read. Includes the full fraction chart below.
Millimetres convert with one division: inches = mm ÷ 25.4. For centimetres it is inches = cm ÷ 2.54. So 20 mm ÷ 25.4 = 0.7874 inches.
Decimals are exact, but nobody's ruler shows 0.7874 — it shows fractions. The converter rounds to the nearest 1/32 of an inch (25/32 for 20 mm), which is close enough for woodworking, sewing and sizing small parts. The chart below uses finer 1/64 steps.
| Millimetres | Centimetres | Inches (decimal) | Nearest 1/64 fraction |
|---|---|---|---|
| 1 mm | 0.1 cm | 0.0394 in | ≈ 3/64 in |
| 2 mm | 0.2 cm | 0.0787 in | ≈ 5/64 in |
| 3 mm | 0.3 cm | 0.1181 in | ≈ 1/8 in |
| 4 mm | 0.4 cm | 0.1575 in | ≈ 5/32 in |
| 5 mm | 0.5 cm | 0.1969 in | ≈ 13/64 in |
| 6 mm | 0.6 cm | 0.2362 in | ≈ 15/64 in |
| 7 mm | 0.7 cm | 0.2756 in | ≈ 9/32 in |
| 8 mm | 0.8 cm | 0.3150 in | ≈ 5/16 in |
| 9 mm | 0.9 cm | 0.3543 in | ≈ 23/64 in |
| 10 mm | 1 cm | 0.3937 in | ≈ 25/64 in |
| 12 mm | 1.2 cm | 0.4724 in | ≈ 15/32 in |
| 15 mm | 1.5 cm | 0.5906 in | ≈ 19/32 in |
| 20 mm | 2 cm | 0.7874 in | ≈ 25/32 in |
| 25 mm | 2.5 cm | 0.9843 in | ≈ 63/64 in |
| 30 mm | 3 cm | 1.1811 in | ≈ 1 3/16 in |
| 40 mm | 4 cm | 1.5748 in | ≈ 1 37/64 in |
| 50 mm | 5 cm | 1.9685 in | ≈ 1 31/32 in |
| 75 mm | 7.5 cm | 2.9528 in | ≈ 2 61/64 in |
| 100 mm | 10 cm | 3.9370 in | ≈ 3 15/16 in |
Measuring something tiny and want to see the size, not just the number? Our 2 mm visual guide shows it against a coin you already own.
Exactly 25.4 mm make 1 inch, by international definition. The reverse of this converter is inches × 25.4 = mm.
20 mm = 0.7874 inches. To the nearest 1/32 that is 25/32 in; to the nearest 1/16 it is 13/16 in (slightly less precise).
Metric values rarely land on a tidy fraction — 20 mm falls between 3/4 in (19.05 mm) and 13/16 in (20.64 mm). Charts round to the nearest mark, which is why the decimal is shown alongside.
Almost — just divide by 2.54 instead of 25.4, because 1 cm = 10 mm. 10 cm = 3.937 inches.