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Tire Size Calculator

Calculate tire diameter, circumference, sidewall height, and revolutions per mile based on tire width, aspect ratio, and rim size.

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Applications

Essential for car enthusiasts and mechanics when changing wheels or tires. Use it to ensure new tire sizes won't negatively hit your speedometer reading or clearance.

Tire Geometry Math

Diameter is calculated as Rim Diameter + 2 × (Width × Aspect Ratio). We convert rim inches to millimeters (25.4mm per inch) for all internal geometric calculations.

Fun Fact: If you increase your tire diameter by just 1 inch without re-calibrating, your speedometer might read 60mph when you're actually doing nearly 63mph!

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