How to Calculate Gear Ratio?

How do you find the Gear Ratio?

Gear Ratio Calculation

Gear ratio is the measurement of ratio of rotational speed of any two gears, when they intertwine with each other. It is calculated by counting the number of teeths in the drive gear and the driven gear. Total number of teeth in the gear will be proportional to the radius of gear pitch circle.

Formula :
Gear Ratio = T2 / T1
Where,
T1 = Number of gears on the drive gear
T2 = Number of gears on the driven gear

Step 1: Lets us assume, that the number of gears in the drive and driven gear is 15 teeth and 30 teeth. What is the Gear Ratio?
T1 - 15 teeth
T2 - 30 teeth

Step 2: Gear Ratio = T2 / T1
= 30 / 15
= 2 / 1
Hence, the gear ratio is 2:1

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