🛞 Tire Size Calculator
Enter your tire’s sidewall numbers (like 225/50R17) to find its overall diameter, circumference, and revolutions per mile.
Reading a tire size
A tire size like 225/50R17 tells you the tire’s width in millimeters (225), its aspect ratio (50, meaning the sidewall height is 50% of the width), and the wheel diameter in inches (17) that it fits.
How this calculator works
The calculator first finds the sidewall height by multiplying width by the aspect ratio. It doubles that (for the sidewall on both top and bottom of the wheel) and adds it to the wheel diameter to get the tire’s overall diameter. From there it calculates the circumference and estimates how many times the tire rotates per mile driven.
This is useful for comparing replacement tire sizes, checking that a size change won’t throw off your speedometer significantly, or estimating rolling distance per rotation. Always confirm fitment with your vehicle’s manual or a tire professional before buying.