Precision Tire Calculators & Size Guides
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Tire Size Calculator Convert tire size into diameter, width, and revs per mile. Tire Size Comparison Compare two sizes for diameter, clearance, and speedometer change. Wheel Offset Calculator Check offset, poke, and clearance before buying wheels. Tire Diameter Calculator Find tire sizes that match a target overall diameter. Gear Ratio Calculator Restore effective gearing after a tire size change.
Featured tool
Tire Size Comparison Calculator
Compare two tire sizes side by side and see the real difference in diameter, width, sidewall height and speedometer accuracy.
- See size differences instantly
- Understand speedometer impact
- Compare upgrade options clearly
Example comparison
Tire 1 245/70R17
Tire 2 265/70R17
| Metric | Current | New | Difference |
|---|---|---|---|
| Overall diameter | 30.50 in | 31.61 in | +1.10 in |
| Width | 9.65 in | 10.43 in | +0.79 in |
| Sidewall height | 6.75 in | 7.30 in | +0.55 in |
| Circumference | 95.83 in | 99.29 in | +3.46 in |
| Speedometer difference | — | +3.61% | +3.61% |
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Accurate Calculations
Our tools use established tire and wheel formulas to provide clear, consistent comparisons.
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Understand changes in diameter, clearance, speedometer accuracy and effective gearing.
Built for Real Decisions
Compare options before buying tires, wheels or drivetrain parts.