mm to Inches Converter
Convert millimetres to inches and back instantly. 1 inch = 25.4 mm exactly — enter a value to see the live result.
How mm to inches conversion works
mm to inches conversion chart
Based on the exact definition 1 inch = 25.4 mm. Decimal inches are rounded to 3 places; the nearest common fraction (to 1/16") is shown where it is useful.
| Millimetres | Inches (decimal) | Inches (fraction) |
|---|---|---|
| 1 mm | 0.039 in | ~1/32 in |
| 2 mm | 0.079 in | ~5/64 in |
| 3 mm | 0.118 in | ~1/8 in |
| 5 mm | 0.197 in | ~3/16 in |
| 10 mm | 0.394 in | ~3/8 in |
| 12 mm | 0.472 in | ~15/32 in |
| 15 mm | 0.591 in | ~19/32 in |
| 20 mm | 0.787 in | ~25/32 in |
| 25 mm | 0.984 in | ~1 in |
| 30 mm | 1.181 in | ~1 3/16 in |
| 50 mm | 1.969 in | ~1 31/32 in |
| 100 mm | 3.937 in | ~3 15/16 in |
Frequently asked questions
How many mm in an inch?
There are exactly 25.4 millimetres in one inch. This is the international definition agreed in 1959, so it is exact rather than rounded. That also means 1 foot (12 inches) = 304.8 mm and 1 metre = 39.3701 inches.
How do I convert mm to inches?
Divide the number of millimetres by 25.4. For example, 100 mm ÷ 25.4 = 3.937 inches. To go the other way, multiply inches by 25.4 to get millimetres.
How many inches is 10 mm?
10 mm equals about 0.394 inches, which is roughly 3/8 of an inch. As a quick mental estimate, every 25 mm is close to 1 inch.
What is 100 mm in inches?
100 mm is 3.937 inches (100 ÷ 25.4), which is just under 4 inches — about 3 15/16 inches in fractional terms.
Is mm bigger or smaller than an inch?
A millimetre is much smaller than an inch. It takes 25.4 millimetres to make a single inch, so a millimetre is about one twenty-fifth of an inch.