What is Gear Ratio ?

The gear ratio quantifies how gears of different sizes interact to transfer motion and energy. This ratio is primarily determined by measuring the circumference of the gears. For instance, if a smaller gear completes two rotations to make a larger gear rotate once, the gear ratio is 2:1, indicating that the output speed is reduced by half.

This example illustrates a fundamental concept that can be extended to more complex gear systems, where multiple gear pairs are used to convert revolutions per minute (RPM) into torque. Consider a more intricate gear reducer with an additional idler gear placed between the smaller and larger gears.

When calculating the gear ratio, only the drive gear and the driven gear are considered; any intermediate gears do not affect the ratio. To find the gear ratio, count the number of teeth on the drive gear and the driven gear. For example, if the drive gear has 7 teeth and the driven gear has 30 teeth, the drive gear must rotate approximately 4.3 times to make the driven gear complete one rotation.