Tire Size Calculator & Comparison
Enter your current tire size to see equivalent sizes that fit, or compare two sizes directly to find the difference in overall diameter, sidewall height, ground clearance, and speedometer accuracy. Enter sizes as width / aspect / wheel (e.g. 225/45R17). A safe plus-size keeps overall diameter within ±3%.
Find used tire shops and wheel dealers in our SC directory, or decode your VIN for the exact OEM fitment.
Browse SC Directory →Decode My VIN →Common questions
How much tire size difference is safe?
Keep the new tire's overall diameter within ±3% of the original. Beyond that, your speedometer, odometer, ABS and traction control can read incorrectly, and larger tires may rub.
How do I read a tire size like 225/45R17?
225 is the section width in millimeters, 45 is the aspect ratio (sidewall height as a percent of width), and 17 is the wheel diameter in inches.
Do bigger tires make my speedometer wrong?
Yes. A larger overall diameter makes your speedometer read slower than your actual speed. This calculator shows your true speed when the speedometer reads 60 mph.