Tire Size Calculator
Enter tire spec (width mm / aspect % / rim in) to compute overall diameter, circumference (in) and diameter (mm).
Input Data
Results
At a glance:Sidewall height = width × aspect ÷ 100; overall diameter(mm) = rim(in)×25.4 + 2×sidewall; circumference = overall diameter(in)×π.
Formula
sidewallMm = widthMm × aspect ÷ 100.
overallMm = rimInch × 25.4 + 2 × sidewallMm.
diameterIn = overallMm ÷ 25.4; circumferenceIn = diameterIn × π; diameterMm = overallMm.
How to Use
- Enter width (mm), aspect ratio (%) and rim diameter (in).
- Get overall diameter, circumference and diameter (mm).
FAQ
Why compute diameter?
A different overall diameter changes speedometer accuracy, fuel economy and clearance; keep it close to the original spec when upsizing.
What does a larger aspect ratio mean?
A taller sidewall gives a softer ride but slower steering response; a lower one is sharper but harsher.
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References
Content reviewed by the Calculatorism editorial team. Results are for reference only; please refer to the relevant authorities for the official figures.