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Tire Size Converter

Decode tire sizes like 205/55R16 to actual diameter, section width, sidewall height, and circumference.

100% client-side · no upload

How to use

  1. Enter the section width in mm, aspect ratio %, and rim diameter in inches — found on your tire sidewall (e.g. 205/55R16).
  2. All measurements update instantly: sidewall height, overall diameter, and circumference.
  3. Use the results to compare replacement tires or check fitment compatibility.

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Frequently Asked Questions

Is this tire size converter free?
Yes, completely free with no signup and no usage limits.
Does my data leave my device?
No. All calculations run in JavaScript inside your browser. Nothing is sent to any server.
Does it work on mobile?
Yes. The converter is mobile-first and works on iPhone Safari and Android Chrome.
Where do I find my tire size?
Look on the sidewall of your current tire. The format is Width/AspectRatioRRimDiameter — for example, 205/55R16 means 205mm wide, 55% aspect ratio, 16-inch rim.
Why does tire diameter matter?
Overall diameter affects speedometer accuracy, ground clearance, and fender fitment. Changing diameter by more than 3% may cause issues with ABS, traction control, and odometer readings.

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