Tire Size Calculator (Compare Sizes)
Tire size calculator: diameter, sidewall height, circumference and revolutions per mile of any tire, and how a new size changes your speedometer.
D = rim × 25.4 + 2 × width × aspect / 100
How to use this calculator
- Type your input in the box.
- The result updates as you type.
- Use “Copy result” or “Copy link” to share it.
In 225/45R17, 225 is the width in mm, 45 the sidewall as % of width and 17 the rim in inches. Keep the diameter within about ±3 % of the original.
Frequently asked questions
225/45R17 vs 235/40R18?
634.3 vs 645.2 mm (+1.7 %); at an indicated 60 mph you would really go about 61 mph.
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