Tire Size Calculator
Compare two tire sizes to see the difference in overall diameter, circumference, width, and sidewall height — plus how much your speedometer would be off if you switched — then browse real used tires in either size on ChromeDeal.
Need one or two tires only? Find replacement tires instead.
How to Compare Tire Sizes
A tire size like 225/65R17 breaks down into four parts: 225 is the tire's width in millimetres, 65 is the aspect ratio (sidewall height as a percentage of that width), R means radial construction, and 17 is the wheel/rim diameter in inches. The calculator above uses these dimensions to work out and compare each size's overall diameter, circumference, width, and sidewall height.
Understanding the Results
- Overall diameter — how much taller or shorter the whole tire is between the two sizes, which is what actually affects ground clearance and gearing.
- Circumference — how far the tire travels in one full revolution; a larger circumference means fewer rotations to cover the same distance.
- Width — the difference in each tire's section width.
- Sidewall height — the difference in tire height from rim to tread, a factor in ride comfort.
- Speedometer — how a change in overall (rolling) diameter can shift the gap between your indicated and actual road speed, since most vehicles calculate speed from wheel rotation.
Can I Use a Different Tire Size?
This calculator compares tire dimensions — it doesn't determine whether a different size will actually fit or work safely on your specific vehicle. Before switching, verify your manufacturer-approved tire sizes (usually listed on a sticker inside the driver's door or in your owner's manual), along with the load index, speed rating, and wheel/rim compatibility for the new size. Also check physical clearance around the wheel well and suspension, and — especially on AWD or 4WD vehicles — confirm the new size meets your drivetrain's tolerance for size differences between axles, since even a small mismatch can strain those systems.