🚗 Tire Size Calculator
Compare tire sizes and check fitment
| Measurement | Tire 1 | Tire 2 | Difference |
|---|---|---|---|
| Width | 225 mm | 235 mm | 10.00 mm |
| Sidewall Height | 101.25 mm | 94.00 mm | -7.25 mm |
| Overall Diameter | 24.97" | 25.40" | 0.43" |
| Circumference | 78.45" | 79.80" | 1.35" |
| Rev/Mile | 808 | 794 | -14 |
Speedometer Difference
When your speedometer reads 60 mph with Tire 2, your actual speed is:
61.0 mph
Difference: 1.7%
Step-by-Step Calculation
Tire 1: 225/45R17
Sidewall = 225 × 45% = 101.25 mm = 3.99"
Diameter = 17" + 2 × 3.99" = 24.97"
Tire 2: 235/40R18
Sidewall = 235 × 40% = 94.00 mm = 3.70"
Diameter = 18" + 2 × 3.70" = 25.40"
How to Use Tire Size Calculator
- 1Enter your current tire size (e.g., 225/45R17).
- 2Enter the new tire size you are considering.
- 3View the difference in diameter, circumference, speedometer error, and ground clearance change.
About Tire Size Calculator
Compare tire sizes, calculate overall diameter, speedometer error, and sidewall height. This tire size calculator helps you find equivalent tire sizes when upgrading or replacing wheels on your vehicle.
Frequently Asked Questions
What do the tire size numbers mean?
In 225/45R17: 225 is the width in mm, 45 is the aspect ratio (sidewall height as % of width), R means radial, and 17 is the wheel diameter in inches.
How much speedometer error is acceptable?
Most experts recommend staying within 3% of the original tire diameter to keep speedometer readings accurate and avoid clearance issues.