Wheels & tires
Tire Size Calculator
Compare your current and proposed tire sizes before changing wheels or tires.
Reviewed September 8, 2026
Enter your numbers
Calculate your estimate
Current tire
New tire
Your estimate
Diameter difference-0.99%
New overall diameter25.72 in
Ride-height change-0.13 in
Actual speed69.3 mph
Circumference change-0.8 in
Estimate only — actual figures may vary.
Quick answer
Compare tire sizes before fitting them
This calculator converts tire width, aspect ratio and wheel diameter into overall size so you can compare clearance and speedometer change.
The method
Understanding tire dimensions
Sidewall height is width times aspect ratio. Overall diameter adds two sidewalls to the wheel diameter.
Check load and speed ratings.
Confirm wheel-width and physical-clearance requirements.
Large diameter changes affect gearing and speedometer accuracy.
Tire size questions
What tire-size numbers do I enter?
Enter the width in millimeters, aspect ratio percentage and wheel diameter in inches for the current and new tire.
Is matching diameter enough for safe fitment?
No. Also check load rating, speed rating, wheel width, brake clearance, suspension clearance and fender clearance.