Free 4WD calculator
Tire size calculator
Compare two metric tire sizes to estimate diameter, ground-clearance change, speedometer difference and gearing impact.
Calculated dimensions are theoretical. Published manufacturer dimensions can differ by tread, pressure and measuring rim.
Ground clearance
+1.38 in
At indicated 60 mph
65.2 mph
Effective gearing
×0.920
What the numbers mean
Overall diameter is calculated from wheel diameter plus two sidewalls. The ground-clearance change is half of the diameter change because only the radius raises the axle.
Actual speed increases when a larger tire travels farther per revolution. The calculation assumes the speedometer was accurate with the original tire.
Effective gearing shows the multiplier applied to the axle ratio. For example, a 4.10 axle multiplied by 0.92 behaves approximately like a 3.77 ratio at the tire.
This calculator compares dimensions only. It cannot determine whether a tire clears suspension, steering, bodywork or brakes on a specific vehicle.