Convert inches (fraction) to millimeters instantly. Enter a value below, or use the formula and reference table further down the page.
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How to convert inches (fraction) to millimeters
Multiply the value by 25.4.
mm = in × 25.4Example: 10 in = 254 mm.
Inches (fraction) to Millimeters conversion table
| Inches (fraction) (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 |
| 10 in | 254 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1270 mm |
| 100 in | 2540 mm |
Frequently asked questions
How many millimeters is 1 inch?
1 inch equals 25.4 millimeters.
What is the formula to convert in to mm?
To convert in to mm, multiply the value by 25.4. The full formula is: mm = in × 25.4.
How do I convert millimeters back to inches (fraction)?
Use the same calculator above and type your value into the millimeters field instead — it converts in both directions. Or use the reverse formula: in = mm ÷ 25.4.
Is the in to mm conversion exact?
The conversion factor used here (25.4) is the standard internationally defined value. Results on this page are rounded to four decimal places for readability.