Inches to Millimeters Converter
Convert inches to millimeters instantly. One inch equals exactly 25.4 millimeters. Type in either box to convert both ways, then use the chart, worked examples and everyday sizes below.
How to convert inches to millimeters
Worked example: convert 90 inches to millimeters. Using millimeters ← inches × 25.4, we get 90 × 25.4 = 2,286 mm. To check the result, convert back: 2,286 mm ÷ 25.4 = 90 in.
Inches to millimeters 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 |
| 8 in | 203.2 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 |
| 150 in | 3,810 mm |
| 200 in | 5,080 mm |
| 250 in | 6,350 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
Millimeters to inches (reverse)
| Millimeters (mm) | Inches (in) |
|---|---|
| 1 mm | 0.03937008 in |
| 2 mm | 0.07874016 in |
| 5 mm | 0.1968504 in |
| 10 mm | 0.3937008 in |
| 20 mm | 0.7874016 in |
| 50 mm | 1.968504 in |
| 100 mm | 3.937008 in |
| 250 mm | 9.84252 in |
| 500 mm | 19.68504 in |
| 1,000 mm | 39.37008 in |
About the inch and the millimeter
The inch is an imperial and US customary unit equal to one twelfth of a foot. It is used for screen sizes, tire and wheel dimensions, plumbing pipes, lumber and many tools in the US, UK and Canada.
A millimeter (millimetre) is one thousandth of a meter and is the everyday unit for small parts: screw diameters, phone thickness, rainfall totals and camera sensor sizes. A credit card is 0.76 mm thick, which gives a feel for the scale.
One inch equals 25.4 millimeters, which makes the inch the longer unit of the two.
Everyday sizes in inches and millimeters
| Everyday example (approximate) | In inches | In millimeters |
|---|---|---|
| The thickness of a credit card | 0.029921 in | 0.76 mm |
| The long side of an A4 sheet of paper | 11.693 in | 297 mm |
| A typical adult's height | 66.929 in | 1,700 mm |
| A standard interior door | 80 in | 2,032 mm |
| A double-decker bus length | 433.07 in | 11,000 mm |
| An Olympic swimming pool | 1,968.5 in | 50,000 mm |
Inches to millimeters FAQ
How many millimeters are in one inch?
One inch equals exactly 25.4 millimeters. In the other direction, one millimeter equals 0.039370079 inches.
How do I convert inches to millimeters without a calculator?
convert 90 inches to millimeters. Using millimeters ← inches × 25.4, we get 90 × 25.4 = 2,286 mm. To check the result, convert back: 2,286 mm ÷ 25.4 = 90 in. For a quick estimate, round the factor to 25. Then 90 in is about 2,250 mm, compared with the exact 2,286 mm (an error of 1.6%). That is close enough for planning, but use the calculator above when the number matters.
What is the long side of an A4 sheet of paper in millimeters?
The long side of an A4 sheet of paper is about 11.693 inches, which is 297 millimeters. Treat that as an approximate everyday figure rather than an official measurement.
Are the inches and millimeters the same in every country?
Since the 1959 international agreement the inch is exactly 25.4 millimeters in the US, UK, Canada and Australia. The millimeter is exactly 0.001 m in every country that uses the metric system.