Tire Size Calculator

Compare different tire sizes, calculate speedometer accuracy, and see how tire changes affect your vehicle's performance and appearance.

Reviewed August 29, 2026 · Calculation methodology · Inputs stay in your browser

Width (mm) The width of your tire in millimeters.

Width (mm) The width of the new tire in millimeters.

Aspect Ratio (%) The aspect ratio (height as % of width).

Aspect Ratio (%) The aspect ratio of the new tire.

Rim Diameter (inches) The diameter of your wheel in inches.

Rim Diameter (inches) The diameter of the new wheel in inches.

Current Speed Reading (mph/km/h)

Enter a speed to calculate speedometer accuracy.

Tire Size Tips

It's generally recommended to stay within +/- 3% of your original tire's overall diameter.
A larger diameter tire will make your speedometer read slower than your actual speed.
Wider tires may provide better grip but can reduce fuel economy and increase noise.
Lower profile tires (smaller aspect ratio) can improve handling but may provide a harsher ride.
Always ensure that new tires have adequate load and speed ratings for your vehicle.