Light Truck Tire Calculator

Enter the original tire size then enter the desired replacement size, aspect ratio and wheel diameter. For informational purposes only, the following is an example to help to decode a tire size like 195/70R15. The 235 is the tire width in millimeters, measured from the bottom of the bead to the bottom of the bead, the 75 is the sidewall aspect ratio, the ratio of sidewall height to tire width at the tread (indicating that the sidewall height is 75% of the tread width), and the 15 is the wheel rim diameter in inches. Click on Calculate for the information concerning the new tire diameter compared to the original, and speedometer differences due to tire size changes to be displayed.

Stock Original Tire Size
Desired Replacement Size
Tire Width Aspect Ratio Wheel Diameter
    
Calculated Results
Original Tire Diameter
New Tire Diameter
Difference = 
Corrected Speedometer Values
20 MPH Indicated
Actual
25 MPH Indicated
Actual
30 MPH Indicated
Actual
35 MPH Indicated
Actual
40 MPH Indicated
Actual
45 MPH Indicated
Actual
50 MPH Indicated
Actual
55 MPH Indicated
Actual
60 MPH Indicated
Actual
65 MPH Indicated
Actual
70 MPH Indicated
Actual
75 MPH Indicated
Actual
80 MPH Indicated
Actual
85 MPH Indicated
Actual
90 MPH Indicated
Actual