Understanding your calculation
Method, example and limitations
How the calculation works
A tire diameter combines wheel diameter with two sidewalls. Sidewall height is tire width multiplied by the aspect ratio; convert millimeters to inches before adding the rim diameter.
Example to check
For 205/55 R16, a sidewall is 205 × 0.55 = 112.75 mm. Overall diameter is about 24.88 inches.
Before using the result
A calculated fit is not approval for a vehicle. Check rim compatibility, clearance, load and speed ratings, and manufacturer guidance before changing tires.