Vehicles & Transport calculator
What Wheel Size Fits My Car?
Use your measurements for current tyre overall diameter, new wheel rim diameter, and new tyre sidewall height to find wheel/tyre overall diameter change.
Enter your measurements
To work out what wheel size fits my car, begin with current tyre overall diameter, new wheel rim diameter, and new tyre sidewall height. The calculator produces wheel/tyre overall diameter change from the measurements that actually control the result.
- Current tyre overall diameter — Required
- New wheel rim diameter — Required
- New tyre sidewall height — Required
- Allowed overall diameter change fraction — Required
Wheel/tyre overall diameter change
Enter the measurements above to calculate wheel/tyre overall diameter change.
How the calculation works
V12 calculation: newOverallDiameter=newWheelDiameter+2×newTyreSidewallHeight; diameterChangeFraction=abs(newOverallDiameter-currentOverallTyreDiameter)/currentOverallTyreDiameter; fitPass=diameterChangeFraction≤maxDiameterChange. This is the implementation specification for this calculator.
Worked example
Example: Current tyre overall diameter = 65 cm; New wheel rim diameter = 45.72 cm; New tyre sidewall height = 10 cm; Allowed overall diameter change fraction = 10%. Result: Fits; Diameter Change Fraction = 1.11 cm; New Overall Diameter = 65.72 cm.
Before you decide
Use measured dimensions rather than nominal labels. This page calculates the stated geometry or quantity only; product-specific construction or installation details can still affect the final choice. For what wheel size fits my car, the limiting result on this page is wheel/tyre overall diameter change.
Direct measurement/geometry calculation. No external reference is required for the arithmetic itself; the result is derived only from the user-entered measurements and the formula stored in calculationLogicJson.
Frequently asked questions
What does the Wheel Size Fits My Car calculator tell me?
It returns wheel/tyre overall diameter change from the measurements entered on this page. The calculation is specific to wheel size fits my car, so the result should be compared with the exact product or specification you are considering.
Which measurements should I take for wheel size fits my car?
Measure current tyre overall diameter, new wheel rim diameter, new tyre sidewall height, allowed overall diameter change fraction. Use clear, usable dimensions rather than nominal room or product labels.
Should I round the wheel/tyre overall diameter change?
Keep the calculated value for comparison, then choose a real product that meets or stays within the returned wheel/tyre overall diameter change while allowing for the clearances, tolerances or ratings shown by its manufacturer.