How to convert millimeters to inches
Formula: in = mm ÷ 25.4
Worked example: 10 mm → 10 ÷ 25.4 = 0.393701 in
Divide millimeters by 25.4 to get inches. Common equivalents in a workshop: 3 mm ≈ 1/8 in, 6 mm ≈ 1/4 in, 13 mm ≈ 1/2 in and 19 mm ≈ 3/4 in, which is why metric and imperial wrenches are often swapped.
Millimeters to inches conversion chart
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 mm | 0.0393701 in |
| 2 mm | 0.0787402 in |
| 3 mm | 0.11811 in |
| 4 mm | 0.15748 in |
| 5 mm | 0.19685 in |
| 6 mm | 0.23622 in |
| 7 mm | 0.275591 in |
| 8 mm | 0.314961 in |
| 9 mm | 0.354331 in |
| 10 mm | 0.393701 in |
| 12 mm | 0.472441 in |
| 15 mm | 0.590551 in |
| 20 mm | 0.787402 in |
| 25 mm | 0.984252 in |
| 30 mm | 1.1811 in |
| 40 mm | 1.5748 in |
| 50 mm | 1.9685 in |
| 75 mm | 2.95276 in |
| 100 mm | 3.93701 in |
| 250 mm | 9.84252 in |
| 500 mm | 19.685 in |
| 1,000 mm | 39.3701 in |
What is a millimeter?
The millimeter is one thousandth of a meter. It is the unit of engineering drawings, metric bolts and drill bits, camera focal lengths, jewelry and rainfall in most countries. In the US it shows up on tools, packaging and anything built to metric standards.
What is an inch?
The inch has been exactly 2.54 centimeters since the 1959 international yard and pound agreement, and 12 inches make a foot. It is the US unit for screen diagonals, lumber, pipe and tire sizes, rainfall and most short lengths.