How to use it
- Enter tire width in millimeters.
- Enter aspect ratio and rim diameter in inches.
- Calculate the theoretical diameter, circumference and revolutions.
Tire Size Calculator
Calculate tire geometry from width, aspect ratio and rim diameter.
Important: This calculator provides estimates only. It is not safety, legal, mechanical, or professional automotive advice. Always follow manufacturer specifications and consult a qualified professional when needed.
About the Tire Size Calculator
This geometry calculator translates the common width, aspect-ratio and rim notation into theoretical dimensions.
Formula
Sidewall height equals width × aspect ratio ÷ 100. Overall diameter adds two sidewalls to the rim diameter converted to millimeters.
Example
A 225/45 R18 tire has a 101.25 mm sidewall and a theoretical overall diameter near 659.7 mm.
Notes
The result does not establish vehicle fitment or compatibility. Confirm approved specifications, load and speed requirements with the manufacturer or a qualified professional.