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Tire Size Calculator

Calculate tire diameter, sidewall, circumference, revolutions, alternative wheel sizes, or compare two tires and speedometer readings.

Tire Size Calculator

ExampleSample values — edit any field to see your result.

mm
in
Change to a new wheel size?
in

Used when wheel-size alternatives are requested.

Results update as you type.

Tire Height (Diameter)

31.6 in / 803 mm

Estimated result

Wheel Size
17 in / 432 mm
Sidewall Height
7.3 in / 186 mm
Tire Width
10.4 in / 265 mm
Tire Circumference
99.3 in / 2,522 mm
Revolutions per Mile
638.1
Revolutions per Kilometer
396.5
Tire Height (Diameter)31.6 in / 803 mm

Decode a tire size into diameter, sidewall, circumference, and revolutions. Request dimensionally similar sizes for another wheel or compare two tires and their speedometer effect.

Formula

sidewall mm = width × aspect / 100 and diameter mm = wheel inches × 25.4 + 2 × sidewall. Circumference is π × diameter.

Examples

265/70R17

The tire is about 31.6 inches (803 mm) tall with a 7.3-inch sidewall and 99.3-inch circumference, making about 638.1 revolutions per mile.

Frequently asked questions

What does 265/70R17 mean?
The tire is 265 mm wide, its sidewall is 70% of that width, R indicates radial construction, and it fits a 17-inch wheel.
How is tire diameter calculated?
Diameter is wheel diameter converted to millimeters plus two sidewalls, where each sidewall is width times aspect ratio.
What does the comparison mode show?
It compares dimensions and revolutions, then shows the actual speed of tire 2 when the speedometer is calibrated for tire 1.
Are alternative sizes automatically safe?
No. The table only identifies dimensionally similar sizes within about 3% diameter. Vehicle clearance, load, speed rating, wheel width, and manufacturer requirements still matter.

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