Tire Size Calculator

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Tire Size Calculator

Compare two tire sizes and see how they affect diameter, circumference and speedometer readings.

Enter the width, aspect ratio and wheel diameter for your current tire and your new tire.

Current Tire

Width (mm)

Aspect Ratio (%)

Wheel Diameter (in)

New Tire

Width (mm)

Aspect Ratio (%)

Wheel Diameter (in)

Speedometer Reading (mph)

Tire Comparison

Current Diameter —

New Diameter —

Current Circumference —

New Circumference —

Current Revs/Mile —

New Revs/Mile —

Diameter Difference —

Actual Speed —

💡 Fitment Note

Enter both tire sizes above to compare them.

Important: Tire dimensions can vary slightly by manufacturer and model. Always verify actual tire specifications and vehicle clearance before changing tire sizes.

How to Use the Tire Size Calculator

This Tire Size Calculator helps you compare two tire sizes and see the difference in overall diameter, circumference, revolutions per mile and estimated speedometer reading.

Enter the width, aspect ratio and wheel diameter for your current tire, then enter the same information for the new tire. The calculator will show how much the overall tire diameter changes and how that difference may affect your indicated vehicle speed.

Why Tire Size Matters

Changing tire size can affect speedometer accuracy, gearing, ground clearance and vehicle fitment. Even tires with the same listed size can vary slightly between manufacturers, so always verify the actual tire specifications and available clearance on your vehicle.

Tire Size Calculator