inches to mm
Inches to Millimeters: mm = in × 25.4. Type a number and read the answer straight off the scale.
inches to mm chart of common values
| Inches | Millimeters |
|---|---|
| 0.0625 in | 1.59 mm |
| 0.125 in | 3.17 mm |
| 0.1875 in | 4.76 mm |
| 0.25 in | 6.35 mm |
| 0.3125 in | 7.94 mm |
| 0.375 in | 9.53 mm |
| 0.5 in | 12.7 mm |
| 0.625 in | 15.88 mm |
| 0.75 in | 19.05 mm |
| 0.875 in | 22.23 mm |
| 1 in | 25.4 mm |
| 1.25 in | 31.75 mm |
| 1.5 in | 38.1 mm |
| 2 in | 50.8 mm |
| 2.5 in | 63.5 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 |
How to convert inches to millimeters
The formula
mm = in × 25.4. The factor is exact by definition, so the answer terminates.
Worked through for 1
Multiply 1 by 25.4. The result is 25.4 mm. Rounded, that is 25.4 mm.
In your head
Multiply by 25, then add 2% more: 2 in → 50 + 1 = 51 mm (exactly 50.8 mm).
More inches to mm
The other way: mm to inches.
Questions
What is the formula for inches to mm?
mm = in × 25.4. One inch is 25.4 millimeters.
How can I estimate it in my head?
Multiply by 25, then add 2% more: 2 in → 50 + 1 = 51 mm (exactly 50.8 mm).
Where do the conversion factors come from?
The pound and the inch were defined in metric units by the 1959 international yard and pound agreement: one pound is exactly 0.45359237 kg and one inch is exactly 2.54 cm.