Convert Inches to Millimeters
20 in = 508 mm
mm = in × 25.4Convert inches to millimeters instantly — type in either box and it works both ways.
How to convert inches to millimeters
To convert inches to millimeters, multiply the number of inches by 25.4.
mm = in × 25.4
Example: convert 20 in to mm
- 20 × 25.4 = 508
- 20 in = 508 mm
1 in = 25.4 mm and 1 mm = 0.03937 in.
Inches to Millimeters conversion chart
| Inches (in) | Millimeters (mm) |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 5 in | 127 mm |
| 10 in | 254 mm |
| 12 in | 304.8 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 100 in | 2,540 mm |
| 500 in | 12,700 mm |
| 1,000 in | 25,400 mm |
Frequently asked questions
How do you convert inches to millimeters?
To convert inches to millimeters, multiply the number of inches by 25.4. The formula is mm = in × 25.4.
How many millimeters are in one inch?
1 in = 25.4 mm.
How do I convert millimeters back to inches?
Use the reverse formula: in = mm ÷ 25.4. For example 1 mm = 0.03937 in.
Is this converter free and accurate?
Yes. It is free, uses exact internationally defined conversion factors, and runs in your browser — nothing you type is sent anywhere.
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