MM ↔ Inches Converter
Convert millimeters to inches or inches to millimeters instantly. Free, accurate length converter.
Common Conversions
| mm | inches |
|---|---|
| 1 mm | 0.0394 in |
| 10 mm | 0.3937 in |
| 25.4 mm | 1 in (exact) |
| 100 mm | 3.937 in |
| 304.8 mm | 12 in (1 ft) |
How to Convert Millimeters to Inches
One inch is exactly 25.4 millimeters. To convert mm to inches, divide by 25.4. Formula: inches = mm ÷ 25.4. To convert inches to mm, multiply by 25.4. Formula: mm = inches × 25.4.
How many mm are in an inch?
There are exactly 25.4 millimeters in one inch. This is an exact definition, not an approximation. It was standardized internationally in 1959.
What are common mm to inches conversions for hardware?
Common hardware sizes (approximate): 3 mm = 1/8 inch, 6 mm = 1/4 inch, 10 mm = 3/8 inch, 13 mm = 1/2 inch, 19 mm = 3/4 inch, 25 mm = 1 inch. These are frequently used for bolts, drill bits, and wrench sizes.
Why do some countries use mm and others use inches?
Most of the world uses the metric system (millimeters, centimeters, meters), while the United States, Liberia, and Myanmar still primarily use imperial units (inches, feet, yards). Many industries like engineering, manufacturing, and science use metric globally regardless of country.