📏 Inches to Millimeters Converter
Convert inches (in) to millimeters (mm) instantly, with the formula, a worked example and a conversion table.
Quick answer: 1 inch (in) = 25.4 millimeters (mm). Formula: mm = in × 25.4.
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Inches to Millimeters Converter inputs
Result
Inches to Millimeters conversion table
| Inches (in) | Millimeters (mm) |
|---|---|
| 0.1 in | 2.54 mm |
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 100 in | 2,540 mm |
| 1,000 in | 25,400 mm |
Other length conversions
in to mmin to cmin to min to kmin to ftin to ydin to miin to nmi
How to convert inches to millimeters
Multiply the number of inches by 25.4 to get millimeters: mm = in × 25.4.
Example: 5 in = 127 mm.
The inch (in) and the millimeter (mm) are both units of length. Need the opposite direction? Use the mm to in converter.
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Metric and imperial units
The metric system (SI) is used by almost every country and by science worldwide. Its units scale by powers of ten – 1 kilometer is 1,000 meters, 1 meter is 100 centimeters – which makes conversions inside the system easy. The imperial and US customary systems (inches, feet, pounds, gallons) are still used daily in the United States and partly in the UK.
Since 1959 the inch has been defined as exactly 2.54 centimeters and the pound as exactly 0.45359237 kilograms, so conversions between the two systems are exact. Note that a US gallon (3.785 L) and an imperial gallon (4.546 L) are different – choose the right one above.
This converter covers 10 categories and 66 units: length, weight, temperature, volume, area, speed, time, data, energy, pressure.
Frequently asked questions
How many millimeters are in a inch?
1 inch = 25.4 millimeters.
How do I convert inches to millimeters?
Use the formula mm = in × 25.4. For example, 5 in = 127 mm.
How do I convert millimeters back to inches?
1 millimeter = 0.039370079 inches. Use the mm to in converter linked on this page.
Are these conversions exact?
Yes – all factors use the internationally defined values (for example 1 inch = 2.54 cm exactly, 1 pound = 0.45359237 kg exactly). Results are rounded to 8 significant digits for display.