Gearing calculator
Compare your current gearing (A) with a planned change (B). The result tells you how much taller or shorter B is.
Compare two setups
Final drive ratio = (spur ÷ pinion) × internal reduction. Lower ratio = taller gearing.
Enter both setups to compare.
Reading the result
A lower final drive ratio is "taller" gearing: more theoretical top speed, slower acceleration and more motor heat. A higher ratio is "shorter": quicker acceleration and cooler running, less top speed.
Internal reduction is the fixed ratio inside the transmission/diffs. Use 1 if your spur drives the wheels directly or you only want the spur/pinion ratio.
Speed changes shown here are theoretical and unloaded. Actual change depends on load, battery and traction.