Tire Aspect Ratio Calculator

A tire's aspect ratio tells you how tall the sidewall is relative to the tire's width — a number that affects ride comfort, handling, and whether a replacement tire will actually fit your car. Enter your tire width, aspect ratio, and rim diameter into the Tire Aspect Ratio Calculator, then select your preferred unit system to get the sidewall height, overall diameter, circumference, and revolutions per mile.

mm

Width of the tire in millimeters

%

Sidewall height as percentage of width

inches

Diameter of the rim in inches

Results

Sidewall Height

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Overall Diameter

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Circumference

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Revolutions per Mile

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Frequently Asked Questions

How is tire aspect ratio calculated?

Tire aspect ratio is the percentage of the tire's sidewall height relative to its width. For example, if a tire is 225mm wide with a 60 aspect ratio, the sidewall height is 60% of 225mm, which equals 135mm.

What does the aspect ratio number mean on a tire?

The aspect ratio is the two-digit number after the tire width in tire size markings. It represents the tire's sidewall height as a percentage of the tire's width. Lower numbers mean shorter sidewalls and typically better handling.

How do I read tire size markings?

Tire sizes are written as width/aspect ratio/rim diameter. For example, 225/60R16 means 225mm width, 60% aspect ratio, and 16-inch rim diameter. The 'R' indicates radial construction.

What happens if I change my tire's aspect ratio?

Changing aspect ratio affects ride comfort, handling, and speedometer accuracy. Lower aspect ratios provide better handling but harsher ride. Higher ratios offer more comfort but less precise steering response.

How does aspect ratio affect overall tire diameter?

Aspect ratio directly impacts overall tire diameter. The total diameter equals rim diameter plus twice the sidewall height. Changing aspect ratio while keeping width constant will change the overall diameter.

Can I use different aspect ratios on the same rim?

Yes, but you must maintain similar overall diameter to avoid speedometer errors and clearance issues. Use a tire size calculator to compare different combinations before making changes.

What is the most common tire aspect ratio?

Common aspect ratios range from 40-70%. Performance tires typically use 40-55%, standard passenger tires use 60-65%, and SUV/truck tires often use 65-70% for better ride comfort and load capacity.