Tire Size & Diameter Comparison
Everyday & OtherCompare automotive tire sizes, overall wheel diameter, sidewall height, circumference, and speedometer reading errors when upgrading wheels and tires.
Overall tire diameter · Sidewall: 3.99 in (101.3 mm)
About this calculator
When upgrading wheels or installing aftermarket tires on cars and trucks, changing tire diameter alters the vehicle's speedometer calibration, odometer tracking, and gear ratio performance.
This calculator compares stock vs new tire specifications (e.g. 225/45R17 vs 245/40R18), computing differences in sidewall height, total rolling diameter, circumference, and actual speed at 60 MPH.
How It Works & Formula
Sidewall Height = Width (mm) × (Aspect Ratio / 100). Total Diameter = (2 × Sidewall Height / 25.4) + Rim Diameter (inches). Circumference = π × Diameter. Speedometer Error (%) = (New Diameter - Old Diameter) / Old Diameter × 100%.
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