About Sidewall Math

Sidewall Math does the arithmetic behind tire sizes. A size such as 225/65R17 hides a diameter, a sidewall height and a circumference that decide how a new size will change your speedometer and ground clearance. Our calculators show every step, and our guides explain the sidewall codes using NHTSA and tire maker information.

We do not tell you what fits a specific vehicle. Fitment depends on wheel offset, brakes, suspension and body clearance, and the approved sizes are on your vehicle's tire placard and in the owner's manual.

Who runs the site

Sidewall Math is a small independent website run by the Sidewall Math editorial team. We are not a manufacturer, retailer, government agency or professional service, and nobody pays us to feature a product or brand. The site launched on Nov 11, 2026.

We do not put names, job titles or credentials on our pages that we cannot back up. Instead, every page shows what it is based on: the formula behind each calculator and a list of the official or reputable sources we checked, with the date we checked them.

How the tools work

Every calculator runs in your browser. Nothing you type is sent to us. Trackers and logs save to your own device (your browser's local storage), so they stay private and disappear if you clear your browser data. There are no accounts.

How the site is paid for

We plan to support the site with advertising in the future. No ads are shown yet.

Some guides contain a small number of clearly marked links to Amazon search results. As an Amazon Associate I earn from qualifying purchases. See our affiliate disclosure.

Get in touch

Corrections and suggestions are welcome on our contact page. Read how we check facts for our standards.