Tire Size Calculator
Compare two tire sizes to see the change in overall diameter and speedometer accuracy.
Assumptions used in this calculation
- ISO tire-code formula: Overall diameter uses the standard ISO metric tire-code formula (rim diameter in inches plus twice the sidewall height derived from width × aspect ratio); it doesn't account for manufacturer variation in actual tire dimensions.
About this calculator
The tire size calculator compares an original and new tire size to find the change in overall diameter and the resulting speedometer error.
Worked example
205/55R16 vs 225/50R17
Result: +3.94% diameter
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