Convert Inches to Millimeters
One inch equals 25.4 millimeters. Type any value to convert inches to millimeters instantly — with a full reference table below.
Convert Inches to Millimeters
Converted in your browser — nothing you enter is sent anywhere.
How to convert Inches to Millimeters
To convert inches to millimeters, multiply by 25.4. One inch equals 25.4 mm, and one millimeter equals 0.0393701 in.
- Take the value in inches — for example 7.5 in.
- Multiply by 25.4 (the number of millimeters in one inch).
- 7.5 × 25.4 = 190.5 mm.
Quick mental estimate: Multiply the number of inches by 25.4 — that is exact.
Inches to Millimeters conversion table
| Inches | Millimeters |
|---|---|
| 1 in | 25.4 mm |
| 2 in | 50.8 mm |
| 3 in | 76.2 mm |
| 4 in | 101.6 mm |
| 5 in | 127 mm |
| 6 in | 152.4 mm |
| 7 in | 177.8 mm |
| 8 in | 203.2 mm |
| 9 in | 228.6 mm |
| 10 in | 254 mm |
| 12 in | 304.8 mm |
| 15 in | 381 mm |
| 20 in | 508 mm |
| 25 in | 635 mm |
| 50 in | 1,270 mm |
| 100 in | 2,540 mm |
| Millimeters | Inches |
|---|---|
| 1 mm | 0.0393701 in |
| 2 mm | 0.0787402 in |
| 3 mm | 0.11811 in |
| 4 mm | 0.15748 in |
| 5 mm | 0.19685 in |
| 6 mm | 0.23622 in |
| 7 mm | 0.275591 in |
| 8 mm | 0.314961 in |
| 9 mm | 0.354331 in |
| 10 mm | 0.393701 in |
| 12 mm | 0.472441 in |
| 15 mm | 0.590551 in |
| 20 mm | 0.787402 in |
| 25 mm | 0.984252 in |
| 50 mm | 1.968504 in |
| 100 mm | 3.937008 in |
About converting Inches to Millimeters
Inches (in) and Millimeters (mm) are both units of length. The exact factor is 1 in = 25.4 mm, so multiply by 25.4 to go from inches to millimeters (or divide to go back).
The conversion runs entirely in your browser. Need the reverse? Use the Millimeters to Inches converter, or the full unit converter for every unit at once.
Real-world length in inches and millimeters
| Example | Inches | Millimeters |
|---|---|---|
| A credit card's width (ISO/IEC 7810) | 3.370079 in | 85.6 mm |
| The long side of A4 paper (ISO 216) | 11.69291 in | 297 mm |
| A US standard door (80 in tall) | 80 in | 2,032 mm |
| A football pitch (FIFA recommended length) | 4,133.858 in | 105,000 mm |
“≈” marks typical values; the rest are defined or measured figures.
The units
Exactly 25.4 mm (1/12 of a foot).
Used for: US and UK screen sizes, tyres, timber and body measurements.
One thousandth of a metre.
Used for: Engineering drawings, rainfall, screen and jewellery sizes.
Every length factor here is exact: the inch has been defined as exactly 25.4 mm since the 1959 International Yard and Pound Agreement.