Tire Size Converter
Decode a metric tire size into inches and compare it with another size to see the diameter difference and speedometer effect.
How to use the Tire Size Converter
- Enter your tire size, such as 225/65R17.
- Optionally enter a second size to compare.
- Read the dimensions and difference.
How it works
In 225/65R17, 225 is the section width in millimeters, 65 is the aspect ratio (sidewall height as a percent of width), R means radial construction and 17 is the wheel diameter in inches. Sidewall = 225 × 0.65 = 146 mm (5.76 in), so overall diameter = 17 + 2 × 5.76 = 28.5 in. A different overall diameter changes speedometer readings: a 3% taller tire makes the car go 3% faster than shown.
Common tire sizes
| Size | Diameter | Width | Revs per mile |
|---|---|---|---|
| 205/55R16 | 24.88 in | 8.07 in | 811 |
| 215/60R16 | 26.16 in | 8.46 in | 771 |
| 225/65R17 | 28.52 in | 8.86 in | 707 |
| 235/65R17 | 29.03 in | 9.25 in | 695 |
| 265/70R17 | 31.61 in | 10.43 in | 638 |
| 275/55R20 | 31.91 in | 10.83 in | 632 |
Frequently asked questions
What does 225/65R17 mean?
225 mm wide, sidewall 65% of the width, radial, for a 17-inch wheel.
How much bigger can I go?
Generally within ±3% of the original overall diameter.
Will bigger tires affect my speedometer?
Yes — taller tires make the speedometer read low.
How tall is a 265/70R17 tire?
About 31.6 inches.