FREE · AUTO & TRAVEL
Tire Size Calculator and Comparison.
Compare two tyre sizes: diameter, width, sidewall, circumference, revolutions per km and the speedometer error after changing size.
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How to use Tire Size Calculator and Comparison
Type the current size and an optional new one, metric (205/55R16) or flotation (31x10.50R15). Choose km/h or mph.
How it works
Sidewall = width × aspect ratio; diameter = rim + 2 × sidewall. The speed error is the ratio of diameters.
Example
205/55R16 to 225/45R17 is +0.38 % in diameter; at 100 km/h shown you actually drive 100.4 km/h.
Questions about Tire Size Calculator and Comparison
Is Tire Size Calculator and Comparison free, and do I need an account?
Yes. This tool is free to use in your browser without an account. Processing takes place on your device.
What are the limits and what should I check?
Calculated from the size code; real dimensions vary by brand and pressure. Check legal rules before changing size. Everything is calculated in your browser; nothing you type is uploaded. Review the result before using it in your work.
Is my input sent to a server?
Your input is processed in your browser and is not uploaded by this tool. Files and pasted text are cleared when the page is refreshed. Normal website requests are still required to load the page and its libraries. Read the privacy explanation.