mm to inches converter
This mm to inches converter turns millimeters into inches, in decimals and in fractions to the nearest 1/16, so a metric drill bit, wrench or bolt size reads straight off in US units.
Formula: in = mm ÷ 25.4 25 ÷ 25.4 = 0.98425197
In every unit (30)
- Nanometer25,000,000 nm
- Micrometer25,000 μm
- Centimeter2.5 cm
- Decimeter0.25 dm
- Meter0.025 m
- Decameter0.0025 dam
- Hectometer0.00025 hm
- Kilometer0.000025 km
- Arpent0.00042757 arp
- Inches0.98425197 in
- Inches (fraction)1 in (Fraction)
- Feet0.082021 ft
- Feet + Inch0 ft 1 in
- Yards0.02734033 yd
- Miles0.00001553 mi
- Fathoms INTL0.01367017 fm
- Nautical mile0.0000135 nmi
- Furlong0.00012427 fur
- Chain0.00124274 ch
- Pole0.00497097 p
- Light year2.6425 × 10⁻¹⁸ ly
- Parsec8.1019 × 10⁻¹⁹ pc
- Krabiat4.80030722 Krabiat
- Nio0.00120019 Nio
- Khuep0.1 Kh
- Sok0.05 Sok
- Wa0.0125 Wa
- Sen0.000625 Sen
- Yot0.00000156 Yot
- Ångström250,000,000 Å
How to use the mm to inches converter
Type a size in millimeters and read the inches on the right. The fraction appears just under the result, and the list below adds the "Inches (fraction)" line along with every other length unit. The round button swaps the units to go from inches to mm. A sum such as 12+6.5 works too.
The factor never changes: an inch is exactly 25.4 millimeters, a value fixed in 1959 (NIST). To go from millimeters to inches you divide by 25.4. The mm to inches converter rounds fractions to the nearest sixteenth, the finest mark on a standard US tape measure.
Common values
| mm | in |
|---|---|
| 1 | 0.0394 |
| 2 | 0.0787 |
| 3 | 0.1181 |
| 5 | 0.1969 |
| 6 | 0.2362 |
| 8 | 0.315 |
| 10 | 0.3937 |
| 12 | 0.4724 |
| 15 | 0.5906 |
| 20 | 0.7874 |
| 22 | 0.8661 |
| 25 | 0.9843 |
| 30 | 1.1811 |
| 40 | 1.5748 |
| 50 | 1.9685 |
| 100 | 3.937 |
| in | mm |
|---|---|
| 0.0625 | 1.5875 |
| 0.125 | 3.175 |
| 0.25 | 6.35 |
| 0.375 | 9.525 |
| 0.5 | 12.7 |
| 0.625 | 15.875 |
| 0.75 | 19.05 |
| 1 | 25.4 |
| 1.25 | 31.75 |
| 1.5 | 38.1 |
| 2 | 50.8 |
| 3 | 76.2 |
| 4 | 101.6 |
| 6 | 152.4 |
| 8 | 203.2 |
| 12 | 304.8 |
Drill bits, sockets and screws in fractions
American tools come in fractions: a 1/4 inch drill bit is 6.35 mm, a 1/2 inch socket fits a 12.7 mm nut, and a 3/4 inch one is 19.05 mm. When a manual or a video gives these sizes, the mm to inches converter tells you which metric bit or socket comes closest.
US screws even have their own gauge numbers (#8, #10…). The Screw category of the conversion calculator gives the decimal and fractional diameter for each gauge.
One more everyday use: rain. Weather services in the US report rainfall in inches, and an inch of rain is 25.4 mm of water. For longer lengths such as a screen size, the cm to inches converter is the better fit.