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 Marava Tech. 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.