How to convert inches to millimeters
Formula: mm = in × 25.4
Worked example: 12 in → 12 × 25.4 = 304.8 mm
Multiply inches by 25.4 for millimeters, an exact result. Fractions convert the same way: 3/8 in = 0.375 × 25.4 = 9.525 mm.
Inches to millimeters conversion chart
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127 mm |
| 6 in | 152.4 mm |
| 7 in | 177.8 mm |
| 8 in | 203.2 mm |
| 9 in | 228.6 mm |
| 10 in | 254 mm |
| 12 in | 304.8 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 30 in | 762 mm |
| 40 in | 1,016 mm |
| 50 in | 1,270 mm |
| 75 in | 1,905 mm |
| 100 in | 2,540 mm |
| 250 in | 6,350 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
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.
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.