This inches to millimeters converter gives you the in to mm result instantly, in your browser, with the exact ratio so you can verify it. 1 inch is about 25.4 millimeters, and going the other way, 1 millimeter is 0.0393701 inches. Inches are an imperial unit still common in the United States and the United Kingdom; millimeters are part of the metric system used in most countries.
To convert by hand, multiply the number of inches by 25.4. For example, 10 inches is 254 millimeters and 100 inches is 2,540 millimeters. The table below lists the most requested values, and the converter above accepts decimals for anything in between.
in to mm formula
mm = in × 25.4
1 inch is about 25.4 millimeters. Multiply the value in inches by that factor to get millimeters.
Inches to Millimeters conversion table
| inches | millimeters | Rounded |
|---|---|---|
| 1 in | 25.4 mm | 25.4 |
| 2 in | 50.8 mm | 50.8 |
| 3 in | 76.2 mm | 76.2 |
| 4 in | 101.6 mm | 102 |
| 5 in | 127 mm | 127 |
| 6 in | 152.4 mm | 152 |
| 7 in | 177.8 mm | 178 |
| 8 in | 203.2 mm | 203 |
| 9 in | 228.6 mm | 229 |
| 10 in | 254 mm | 254 |
| 12 in | 304.8 mm | 305 |
| 15 in | 381 mm | 381 |
| 20 in | 508 mm | 508 |
| 25 in | 635 mm | 635 |
| 30 in | 762 mm | 762 |
| 40 in | 1,016 mm | 1,016 |
| 50 in | 1,270 mm | 127 |
| 60 in | 1,524 mm | 1,524 |
| 70 in | 1,778 mm | 1,778 |
| 75 in | 1,905 mm | 1,905 |
| 80 in | 2,032 mm | 2,032 |
| 90 in | 2,286 mm | 2,286 |
| 100 in | 2,540 mm | 254 |
| 150 in | 3,810 mm | 381 |
| 200 in | 5,080 mm | 508 |
| 250 in | 6,350 mm | 635 |
| 300 in | 7,620 mm | 762 |
| 500 in | 12,700 mm | 127 |
| 750 in | 19,050 mm | 1,905 |
| 1,000 in | 25,400 mm | 254 |
Frequently asked questions
How many millimeters are in 5 inches?
5 in = 127 mm. Multiply 5 by 25.4, the number of millimeters in one inch. The converter on this page does the same arithmetic for any value, including decimals.
What is the formula to convert inches to millimeters?
mm = in × 25.4. The factor comes from the definitions of the units: 1 inch is about 25.4 millimeters. Worked example: 12 in = 304.8 mm.
Is 30 in the same as 762 mm?
Yes. 30 in = 762 mm. Rounded to four decimals it is 762 mm.
How do I convert millimeters back to inches?
Divide by 25.4, or multiply by 0.0393701: 1 millimeter is 0.0393701 inches. The millimeters to inches page linked above lists common values the other way.
Is the in to mm conversion exact?
1 inch is about 25.4 millimeters. The ratio is a defined constant but produces a long decimal, so this page rounds to six significant digits, which is more precision than any everyday measurement needs.