Tire Size Calculator
Calculate the overall diameter of a tire from its size.
Result
Results are estimates for general information only and are not professional advice.
Reading tire sizes
A tire code like 205/55R16 means a 205 mm width, a sidewall that is 55% of the width, on a 16-inch rim. This calculator combines those to give the overall tire diameter in millimeters and inches, plus its circumference.
Frequently Asked Questions
What is the Tire Size Calculator?
Calculate the overall diameter of a tire from its size. It runs instantly in your browser and is completely free to use.
What do I need to enter to use the Tire Size Calculator?
The Tire Size Calculator asks for the following values (3): Section width (mm), Aspect ratio (%), Rim diameter (in). Fill them in and the result appears immediately — the calculation runs on your own device, so nothing you type is sent to a server.
How accurate is the Tire Size Calculator?
The Tire Size Calculator uses standard, widely-accepted formulas, so its figures are reliable estimates for everyday planning. They are not a substitute for advice from a qualified professional.
Is the Tire Size Calculator free, and do I need an account?
Yes. The Tire Size Calculator — and every other calculator on Calculatis — is completely free, with no registration, no download and no limit on how often you use it.