Inches to millimeters
1 inch in millimeters
1 in = 25.4 mm
mm = in × 25.4
To convert inches to millimeters, multiply by 25.4. The table below gives the values people look up most often, and the converter works for any number.
Inches to millimeters table
| Inches | Millimeters |
|---|---|
| 1 in | 25.4 |
| 2 in | 50.8 |
| 3 in | 76.2 |
| 4 in | 101.6 |
| 5 in | 127 |
| 10 in | 254 |
| 15 in | 381 |
| 20 in | 508 |
| 25 in | 635 |
| 30 in | 762 |
| 40 in | 1,016 |
| 50 in | 1,270 |
| 75 in | 1,905 |
| 100 in | 2,540 |
| 250 in | 6,350 |
| 500 in | 12,700 |
| 1,000 in | 25,400 |
How the conversion works
The relationship is mm = in × 25.4. Both units measure length, so the conversion is a fixed factor that never changes. The figure is exact rather than approximate: since the international yard and pound agreement of 1959, an inch is defined as exactly 25.4 millimetres and a pound as exactly 0.45359237 kilograms, and every other imperial and US customary unit here is derived from those two.
Common questions
- How many millimeters are in one inch?
- One inch equals 25.4 millimeters. mm = in × 25.4.
- How do you convert inches to millimeters?
- Use mm = in × 25.4. So 10 in is 254 mm.
- How many inches are in one millimeter?
- One millimeter equals 0.03937 inches, which is the reverse of the conversion above.
Related pages
Sources
- Guide for the Use of the International System of Units (SP 811) — NIST (Public domain (US Government))
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures
- Calculated on this page — At One Place