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Tire Size Calculator - Diameter & Circumference
Free tire size calculator. Calculate tire diameter, circumference, and sidewall height from tire size code (e.g., 225/45R17).
Tire Size Calculator
Calculate tire dimensions
Tire Dimensions
Enter your values to see results
and click the "Calculate" button
Tire Size Calculator
Understand tire sizing (e.g., 225/45R17). Calculate diameter for speedometer accuracy and fitment.
Tire Size Decoding
Diameter = (Width × Aspect / 2540 × 2) + Rim
225/45R17: 225mm wide, sidewall is 45% of 225mm, fits 17" rim. R = radial construction.
Frequently Asked Questions
How does tire size affect speedometer?
Larger tires = fewer revolutions = speedometer reads slow. 3% diameter change ≈ 3% speedometer error.
What's the '3% rule' for plus sizing?
When upsizing wheels, keep overall diameter within 3% to maintain speedometer accuracy and avoid rubbing.
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