Tire Size Calculator - Compare Sizes
Compare tire sizes, diameter differences, and speedometer error.
Tool Interface
Tire Size Calculator
Compare two tire sizes: diameter, sidewall, circumference, and speedometer error.
| Spec | Current | New |
|---|---|---|
| Sidewall height | ||
| Overall diameter | ||
| Circumference | ||
| Revs per mile |
How to use
Enter tire sizes in the standard format width/aspectRrim, e.g. 205/55R16 (205 mm wide, 55% aspect ratio, 16 inch rim). Press Compare to see both tires side by side plus the speedometer impact. Reset restores the examples.
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About This Tool
Frequently Asked Questions (FAQ)
What does the tire size calculator compare?
Enter your current and new tire sizes to compare overall diameter, width, sidewall height and circumference side by side.
Will bigger tires affect my speedometer?
Yes. A larger overall diameter makes the speedometer read slower than your actual speed. The calculator shows the exact percentage difference so you know what to expect.
What do the numbers in a tire size mean?
In a size like 205/55R16, 205 is the width in millimeters, 55 is the sidewall height as a percentage of the width, R means radial construction and 16 is the wheel diameter in inches.
How much can I safely change my tire size?
Stay within 3 percent of the original overall diameter. Larger changes can affect gearing, clearance and safety systems.
Is the tire size calculator free?
Yes. It is free to use with no signup and no limits.