About Tire Size Box

Tire Size Box turns tire sizes into real-world measurements and compares them, so you can pick replacement or upgrade sizes with confidence. The site covers 1,148 common car, SUV and light-truck sizes.

How we calculate

• Metric sizes: sidewall = width (mm) × aspect ratio ÷ 100. Overall diameter = wheel diameter + 2 × sidewall, converted at 25.4 mm per inch.
• Flotation sizes (33x12.50R20) state the overall diameter and width directly.
• Circumference = π × diameter. Revolutions per mile = 63,360 inches ÷ circumference.
• Speedometer: real speed = indicated speed × new diameter ÷ original diameter.
• Rim width ranges are estimates based on the usual ratio of rim width to tire width. Always check the tire maker's approved range.
• Load index values follow the standard ISO table in kilograms; pounds are converted.

Limits

These are nominal dimensions. Real tires vary by brand, model, tread depth, rim width and inflation, and loaded tires are slightly shorter. Before changing size, check your vehicle's tire placard, clearance and load requirements with a tire professional.

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