Inches to millimeters
millimeters = inches × 25.4
Reverse: millimeters to inches
How to convert inches to millimeters
One inch is 25.4 millimeters, so multiply the number of inches by 25.4. For example, 20 inches is 20 × 25.4 = 508 millimeters. To go back, divide by the same number, or multiply by 0.03937008.
Quick estimate
Multiplying by about 30 gets within 18.1% of the exact answer, which is enough to check that a result makes sense.
Where it comes up
Length conversions come up in DIY and building plans, running and cycling distances, maps, clothing sizes and travel between countries that use metric and imperial units.
| inches | millimeters |
|---|---|
| 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 |
| 11 in | 279.4 mm |
| 12 in | 304.8 mm |
| 13 in | 330.2 mm |
| 14 in | 355.6 mm |
| 15 in | 381 mm |
| 16 in | 406.4 mm |
| 17 in | 431.8 mm |
| 18 in | 457.2 mm |
| 19 in | 482.6 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 30 in | 762 mm |
| 40 in | 1,016 mm |
| 50 in | 1,270 mm |
| 60 in | 1,524 mm |
| 70 in | 1,778 mm |
| 75 in | 1,905 mm |
| 80 in | 2,032 mm |
| 90 in | 2,286 mm |
| 100 in | 2,540 mm |
| 120 in | 3,048 mm |
| 150 in | 3,810 mm |
| 200 in | 5,080 mm |
| 250 in | 6,350 mm |
| 300 in | 7,620 mm |
| 400 in | 10,160 mm |
| 500 in | 12,700 mm |
| 750 in | 19,050 mm |
| 1,000 in | 25,400 mm |
| 1,500 in | 38,100 mm |
| 2,000 in | 50,800 mm |
| 5,000 in | 127,000 mm |
| 10,000 in | 254,000 mm |
Questions
How many millimeters are in a inch?
25.4 millimeters.
How do I convert inches to millimeters in a spreadsheet?
Put the value in A1 and type =A1*25.4, then fill the formula down the column.
Are the values in the table exact?
They are calculated from the exact definitions of the units and rounded only for display. Open any row for the full working.