This rpm calculator allows you to easily calculate the rpm of a gearbox. You just need to know the internal gearing of your motors and the gear ratio you have. If you have a direct drive, just put 1:1 for the ratio. The math is below.
The Gear Ratio
The gear ratio is calculated as follows: input2 / input1. This converts a ratio into a decimal which is easier to use in calculations.
The RPM Calculations
The equation to calculate the rpm is below.
rpm of motor based on internal gearing*ratio