Home / Tire Size Calculator
Compare two tire sizes and see the diameter difference and how far off the speedometer will read. The size is printed on the tire sidewall, like 225/45R17.
Diameter = rim + 2 × (width × aspect ÷ 100) ÷ 25.4. A bigger diameter makes the speedometer read slow; a smaller one makes it read fast. Stay within about 3% of the original diameter so the speedometer, ABS and traction control keep working right.
