Calculate tire diameter, sidewall height, circumference, revolutions per mile, speedometer difference, and tire size comparison. Use this tire size calculator to compare your current tire size with a new tire size.
Single tire size:
Enter tire width, aspect ratio, and wheel diameter to calculate sidewall height, overall diameter, circumference, and revolutions per mile.
Compare tire sizes:
Enter a current tire size and a new tire size to compare diameter, circumference, sidewall height, and percent difference.
Speedometer difference:
The calculator estimates actual speed based on the difference between current and new tire diameter.
Revolutions per mile:
Shows how many times the tire rotates over one mile based on tire circumference.
A tire size calculator helps compare different tire sizes before changing wheels or tires.
It can help estimate speedometer change, ride height change, wheel gap change, tire circumference, and whether a new tire size is close to the original size.
Your result shows tire diameter, sidewall height, circumference, revolutions per mile, diameter difference, percent difference, speedometer difference, and actual speed estimate. These are estimates based on the tire size values you enter.
Convert the sidewall height to inches, double it, then add the wheel diameter.
225 is the tire width in millimeters, 65 is the sidewall aspect ratio, and 17 is the wheel diameter in inches.
Many tire changes try to stay within about 3% of the original diameter, but fitment depends on the vehicle, wheels, clearance, and manufacturer guidance.
Yes. A larger tire travels farther per rotation and can make actual speed higher than the speedometer reading. A smaller tire can do the opposite.