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Tire Size Calculator
Overall diameter, sidewall height, circumference and revolutions per mile from a metric tire spec (e.g. 225/45R17).
Inputs
Tire Size Calculator
Result
Overall diameter
24.97 in
- Overall diameter
- 634 mm
- Sidewall height
- 101.3 mm
- Circumference
- 1.993 m
- Revs per km
- 501.8
- Revs per mile
- 807.6
How it's calculated
diameter = wheel + 2 × (width × ratio/100) / 25.4; circumference = π × diameter
Common questions
How do I read a tire size like 225/45R17?
225 is section width in mm, 45 is the aspect ratio (sidewall height as a % of width), and 17 is the wheel diameter in inches.
Why does tire size matter for the speedometer?
Speedometers are calibrated for the factory tire diameter. A larger overall diameter makes the car travel farther per revolution, so the speedometer reads lower than the real speed.
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