Inch to MillimeterConverter
Instantly convert Inch (in) to Millimeter (mm). Free, accurate, and easy to use.
How to Convert Inch to Millimeter
To convert Inch (in) to Millimeter (mm), multiply your value by 25.4.
Example: 5 in × 25.4 = 127 mm
What is a Inch?
The inch is a unit of length in the imperial and US customary systems, defined exactly as 2.54 centimeters since the International Yard and Pound Agreement of 1959. It is divided into binary fractions — halves, quarters, eighths, and sixteenths — and remains standard for screen sizes, display resolutions, and construction lumber in the United States. Historically, the inch derived from the width of a human thumb or three barleycorns placed end to end. A US letter sheet of paper measures 8.5 inches wide.
What is a Millimeter?
The millimeter is one thousandth of a meter, making it the smallest SI length unit in routine use. Defined exactly as 0.001 m, it equals roughly 1/25 of an inch. Millimeters are the standard for precision engineering, machining tolerances, and clinical measurements. A standard credit card is about 0.76 mm thick, and a human hair averages 0.06–0.08 mm in diameter.
Inch to Millimeter Conversion Table
| Inch (in) | Millimeter (mm) |
|---|---|
| 0.001 in | 0.0254 mm |
| 0.01 in | 0.254 mm |
| 0.1 in | 2.54 mm |
| 0.5 in | 12.7 mm |
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 20 in | 508 mm |
| 50 in | 1270 mm |
| 100 in | 2540 mm |
| 200 in | 5080 mm |
| 500 in | 12700 mm |
| 1000 in | 25400 mm |
| 5000 in | 127000 mm |
| 10000 in | 254000 mm |
| 50000 in | 1270000 mm |
| 100000 in | 2540000 mm |
| 1000000 in | 25400000 mm |
| 1000000000 in | 2.5400e+10 mm |
Frequently Asked Questions
How do I convert Inch to Millimeter?
Multiply the Inch value by 25.4. Formula: mm = in × 25.4. Example: 10 in = 254 mm.
How many Millimeter are in one Inch?
One Inch (in) equals 25.4 Millimeter (mm).
How many Inch are in one Millimeter?
One Millimeter (mm) equals 0.03937008 Inch (in).
What is the exact conversion factor from Inch to Millimeter?
The conversion factor is 25.4. Multiply any in value by this number to get mm. For the reverse, multiply by 0.03937008.
How do I convert Millimeter back to Inch?
Divide by 25.4, or equivalently multiply by 0.03937008. Formula: in = mm ÷ 25.4.
Is the Inch-to-Millimeter conversion internationally standardized?
Yes. Both units are defined by international standards (SI or the international yard/pound agreement), so the conversion factor 25.4 is exact and universally agreed upon.