Tire Size Calculator
Compare tire dimensions and calculate speedometer error when upgrading sizes.
Results
What is a Tire Size Calculator?
A tire size calculator helps you compare the overall diameter of two tire sizes. This is essential when upgrading or changing wheels to ensure proper fitment and accurate speedometer readings.
How to Use This Calculator
- Enter the width, aspect ratio, and rim diameter for your current (old) tire.
- Enter the same values for the new tire you are considering.
- Click "Compare Tire Sizes" to see diameter difference and speedometer error.
Frequently Asked Questions
How is tire diameter calculated?
Diameter = (width × aspectRatio / 100 × 2 / 25.4) + rimDiameter. The aspect ratio is the sidewall height as a percentage of the width.
What speedometer error is acceptable?
Generally, a difference within 3% is considered acceptable. Larger differences may affect ABS, traction control, and speedometer accuracy.
What is plus sizing?
Plus sizing means fitting a larger wheel with a lower-profile tire while keeping the overall diameter close to stock to maintain performance and accuracy.
Can I use this for any vehicle?
Yes, the calculations are universal for any tire using standard sizing notation (e.g., 205/55R16).