Tire size comparison
Compare nominal tire diameter, circumference, ride-height change and the theoretical speedometer effect of two sizes. Enter the comparison size and indicated speed.
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How it works
Formula
Input and formula key
Your result
Complete the inputs to see your result.
Sources
- Michelin — tire width, aspect ratio and rim diameterSources reviewed: 2026-10-30
- Michelin — approved replacement sizesSources reviewed: 2026-10-30
Assumptions and limitations
Geometry only; no fitment recommendation. Actual rolling radius depends on load, wear and inflation. Excludes load rating, clearances, rim compatibility and vehicle approval. Follow the vehicle maker’s approved sizes.
How to use this tool
Set up the inputs
For a size such as 205/55 R16, enter 205 mm width, 55% aspect ratio and 16 inches rim diameter. Enter the comparison size and indicated speed.
Worked examples
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Compare two tyre sizes by overall diameter
205/55 R16: 16 × 25.4 + 2 × 205 × 0.55 = 631.9 mm. 225/45 R17: 634.3 mm; +0.3798%.
Frequently asked questions
How should I read the result from Tire size comparison?
Positive diameter change means a larger nominal tire. The speed estimate assumes the speedometer was exact with the original size; it is not a calibration certificate.
Processing and privacy
The calculation or transformation runs in your browser. The tool does not send its input values or generated output to an application server. Loading a page still makes infrastructure requests; optional analytics and Google consent messages have separate controls.
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Help and feedback
Consult the linked sources for definitions and reference data. Contact Support if you have a question or notice a problem.
Read about calculation methods · Report a problem to emonster
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