About Tire Size Calculator

Tire Size Calculator is a free tire size calculator. Type a stamp like 275/65R20 and get overall diameter, section width, sidewall, circumference and revolutions per mile. Compare a second size and the drawing shows both outlines plus the speedometer error. The arithmetic runs in your browser. Nothing you type is sent to a server.

The site exists because the useful tools in this niche are either a forum calculator buried in a thread, or a retailer page that exists to sell a tire. We wanted the number, the drawing, and a way off the page. No "shop this size" button.

Geometry is the product. We do not have a per-vehicle fitment dataset and we will not invent one. Diameter and width tell you whether two sizes are in the same family. They do not tell you whether a size clears your fenders. Check the door-jamb sticker and the well before you buy.

Who built it

Madhu Kinnera, as Tire Size Calculator. The formulas are standard tire geometry, the same ones every manufacturer and shop uses: sidewall equals width times aspect ratio, overall diameter equals rim plus two sidewalls.

Contact

Questions or a wrong number? Email hello@tiresizetool.com.