The gear ratio is the ratio of the number of turns the output shaft makes when the input shaft turns once.

Gear ratios are what allow a car to reach a high rate of speed or climb a steep hill.

It is used to measure a wide variety of mechanical items, including clocks, automobiles, farming machines and equipment and more. The gear ratios help determine how well the machine is performing.

**Formula to calculate gear ratio.**

**Example:**

If the driver gear has 20 teeth, and the driven gear has 40, calculate the gear ratio.

Therefore, the gear ratio is 2:1. This means that, for every rotation of the driven gear, the driver gear makes two rotations.