Tire Size Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the tyre width (mm), aspect ratio (%) and rim diameter (in).
- Read the overall diameter, circumference and revolutions per km.
How it works
Sidewall = width × aspect ÷ 100; diameter = rim + 2 × sidewall; circumference = π × diameter.
Worked example
205/55 R16. Overall diameter ≈ 632 mm.
Tips
- Runs entirely in your browser. Your inputs are not saved or transmitted.
Frequently asked questions
How do I read a tyre size?
e.g. 205/55 R16 = 205 mm wide, 55% aspect ratio, 16-inch rim.
Privacy?
Runs entirely in your browser. Your inputs are not saved or transmitted.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.