Tire Size Comparison Calculator
Compare overall diameter, clearance and speedometer effect for two tire sizes.
What would you like to do next?
Compare the geometry of two tire sizes
Enter section width, aspect ratio and rim diameter for a current and proposed tire. The calculator converts both sidewalls into millimeters, adds the wheel diameter and compares overall diameter and circumference. It also shows the estimated actual speed at a user-entered indicated speed and the change in ride height created by half the diameter difference.
Geometry is only one fitment check
A close diameter does not prove that a tire fits. Wheel width and offset, suspension and body clearance, load index, speed rating, braking behavior, calibration, local rules and manufacturer approvals still need review by a qualified provider before a tire or wheel change.
Frequently asked questions
How is tire diameter calculated?
The calculator adds two sidewalls to the rim diameter after converting the rim from inches to millimeters.
Does this confirm wheel fitment?
No. Offset, wheel width, clearance and ratings require separate checks.
Why does actual speed change?
A different circumference travels a different distance for each wheel rotation.