Tire Width Unit Converter
Switch tire width between mm and inches. Use the calculator below. Results update as you type.
How the Tire Width Unit Converter Works
This converter works by dividing millimeters by 25.4 to get inches, or multiplying inches by 25.4 to get millimeters. It converts tire section widths in both directions.
- Enter a width in mm, for example 245.
- Read the width in inches: 9.65 in.
- Read the width in centimeters: 24.5 cm.
- Enter an inch value instead (for example 12.50) to get mm: 317.5 mm.
The Formula
The formula is Width (in) = Width (mm) ÷ 25.4. The reverse formula is Width (mm) = Width (in) × 25.4.
Width (in) = Width (mm) ÷ 25.4 Width (mm) = Width (in) × 25.4 Width (cm) = Width (mm) ÷ 1025.4 is the exact number of millimeters in one inch, set by international agreement in 1959. Worked example: 275 mm ÷ 25.4 = 10.83 in.
Conversion Table
The conversion table converts 20 section widths from 155 mm to 345 mm into inches and centimeters. The table splits into 2 column groups to fit on one screen.
Each 10 mm step adds 0.39 in. A 225 mm tire is 8.86 in wide and a 335 mm tire is 13.19 in wide.
| Width (mm) | Width (in) | Width (cm) | Width (mm) | Width (in) | Width (cm) |
|---|---|---|---|---|---|
| 155 | 6.10 | 15.5 | 255 | 10.04 | 25.5 |
| 165 | 6.50 | 16.5 | 265 | 10.43 | 26.5 |
| 175 | 6.89 | 17.5 | 275 | 10.83 | 27.5 |
| 185 | 7.28 | 18.5 | 285 | 11.22 | 28.5 |
| 195 | 7.68 | 19.5 | 295 | 11.61 | 29.5 |
| 205 | 8.07 | 20.5 | 305 | 12.01 | 30.5 |
| 215 | 8.46 | 21.5 | 315 | 12.40 | 31.5 |
| 225 | 8.86 | 22.5 | 325 | 12.80 | 32.5 |
| 235 | 9.25 | 23.5 | 335 | 13.19 | 33.5 |
| 245 | 9.65 | 24.5 | 345 | 13.58 | 34.5 |
What Is the Tire Width Unit Converter?
The Tire Width Unit Converter is a tool that converts tire section width between millimeters, inches and centimeters. Metric tires print width in mm; flotation tires print it in inches.
Width matters for 3 checks: rim compatibility, inner clearance to the strut or control arm, and outer clearance to the fender lip. Wheel-well measurements are often taken in inches, so a unit conversion is the first step in every clearance check.
Common Uses
This converter has 4 uses: clearance checks, rim matching, cross-system comparisons and spec-sheet reading.
- Check clearance: Compare tire width with measured space in inches or mm.
- Match rims: Compare tire width with rim width in the same unit.
- Compare systems: Line up metric and flotation widths.
- Read spec sheets: Convert published widths into your preferred unit.