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tireClassic tool

Tire Size Calculator

Calculate sidewall height, overall diameter, circumference and revolutions per mile from a tire size.

Use this tire size calculator to work out the final diameter of a size like 205/55R16 without doing the math by hand. Enter width, aspect ratio and rim diameter to see sidewall height, overall diameter, circumference and an estimate of revolutions per distance.

The calculation follows the logic used on the tire sidewall: width is measured in millimeters, aspect ratio is the sidewall height as a percentage of width, and wheel diameter is listed in inches. The tool converts each measurement and combines them into a simple summary.

This estimate is useful for quick comparisons, catalog checks and general fitment planning. If you plan to move away from your vehicle factory size, confirm load rating, clearance and manufacturer guidance before buying.

Common example: 205/55R16 means 205 mm width, a sidewall equal to 55% of that width and a 16-inch wheel.

SummaryEnter width, aspect ratio and rim diameter to calculate the tire size.
Built size—
Sidewall height (mm)—
Sidewall height (in)—
Overall diameter (mm)—
Overall diameter (in)—
Circumference—
Revolutions per km—
Revolutions per mile—
Applied formula—

These are geometric estimates only. They do not replace checks for load index, speed rating, wheel offset or real-world clearance.

Use clear inputs to get a more useful result.