Tire Size Calculator
Calculate tire dimensions, compare sizes, and check speedometer accuracy when changing tire sizes.
Overall Diameter
24.97 in
Inputs
mm
%
in
mm
%
in
Comparison
Sidewall Height
3.99 in
Circumference
78.45 in
Revolutions/Mile
808
Compare Diameter
25.4 in
Size Difference
1.72%
Speedometer Error
1.72%
Diameter Comparison
How to Use This Calculator
- Enter your current tire's Width (mm), Aspect Ratio (%), and Rim Diameter (in) — found on the tire sidewall.
- Enter the comparison tire's width, aspect ratio, and rim diameter in the compare fields.
- Review the Overall Diameter, Sidewall Height, and Circumference for each tire.
- Check the Size Difference (%) and Speedometer Error (%) to understand the impact of a size change.
- A positive speedometer error means your actual speed is higher than displayed.
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