Frequently Asked Questions
Everything you need to know about tire and wheel sizing and how our calculators work.
How accurate are the results?
Calculations use standard tire geometry formulas and are highly accurate for comparison. Real tires can vary slightly by brand and model.
Why don't the values match another website?
Different sites round differently or use slightly different formulas. We show more decimal places and follow standard geometry.
Where does the data come from?
Dimensions are derived from the tire size code (width / aspect ratio / rim) using standard formulas — no proprietary database required.
Is the website free?
Yes. Every tool is completely free with no sign-up and no usage limits.
Can I use it for any type of vehicle?
Yes — cars, pickups, SUVs, and motorcycles. Just enter the tire size printed on the sidewall.
Is there a mobile app?
Not yet, but the site is fully mobile-friendly and works great in any browser. A dedicated app is on our roadmap.
How much can I change my tire size?
A common guideline is to keep the overall diameter within about ±3% of the original, so your speedometer and safety systems stay accurate. Our Tire Size Calculator shows this difference for you.
What is Plus / Minus sizing?
Plus sizing fits a larger wheel with a lower-profile tire (Minus is the opposite), while keeping the overall diameter close to stock. Use our Plus / Minus Sizing tool to compare options.
Do you collect my personal data?
No. The site is static with no accounts, and the values you enter are processed in your browser, never sent to us. Analytics runs only after you accept the cookie consent.
What units do the tools support?
Both metric (millimetres) and imperial (inches). The Unit & Tire Converter switches between them and converts sizes in either direction.