The ratio of a ring and pinion gear set is simply the number of ring gear teeth divided by the number of pinion gear teeth. To use the calculator, count the teeth on each gear and enter them in the appropriate box. Press the Solve button and the ratio appears below. The results can be used in our Transmission Ratio RPM Calculator and RPM Calculator. This also helps confirm the ratio if you lose the box or can’t read the stamping on the gears.