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Free tool

Tire Size Calculator

Compare a new tire size to your stock size — diameter change and speedometer error.

Original (e.g. 225/45R17)

Width

Aspect

Wheel

New

Width

Aspect

Wheel

Repair data & vehicle history for every car.

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© 2026 AutoPros. Calculations are approximate. Confirm fitment, load rating, and clearance before changing tire sizes; a difference over ~3% in diameter can affect speedometer accuracy, ABS, and clearance.