Off-Road Calculators

Differential Gear Ratio Calculator
Calculate your differential gear ratio from RPM, tire size, and desired MPH

Enter the # of Pinion Gear teeth and the # of Ring Gear teeth to find the gear ratio
Find New Gear Ratio with a New Tire Size
Buying bigger or smaller tires? Then you might need to change your gear ratio to keep up! Enter your new tire diameter, your old tire diameter, and your present gear ratio to find out your new gear ratio
Convert P-Metric Tire to Tire Diameter Inches
Convert the funky P-Metric Tire # (Example: 195/75R15) on the side of your tires to the inch equivalent
Speedometer Converter
Find out how changing the tire size affects speedometer accuracy. Enter the diameters of your new and old tires, then enter a target speed and see the difference!
Find MPH
Find the estimated maximum speed based on a target RPM, rearend ratio, and tire size
Find RPM
Find the RPM based on the tire size and, transmission, transfer case, and rearend ratios
Find Overall Crawl Ratio
Figure out your off-road 4x4 crawl ratio based on transmission, axle, and transfer case ratios