What Is Gear Ratio?
What Is Gear Ratio?
A gear ratio is the ratio of the number of teeth on two meshing gears. It describes how one gear's movement affects another.
In the simplest terms, gear ratio is a way to compare the speed and torque between two connected gears. It tells you how many times one gear turns with another.
Formula:
Gear Ratio = Teeth on Driven Gear / Teeth on Driver Gear
Example:
Driver gear: 10 teeth
Driven gear: 30 teeth
Gear Ratio = 30 / 10 = 3:1
This means the driver must rotate 3 times to turn the driven gear once. The output turns slower, but with more force.
How Does Gear Ratio Work?
Gear ratios can do two main things:
Increase torque (turning force)
Increase speed (RPM - revolutions per minute)
But there's a trade-off:
A higher gear ratio (like 3:1) gives more torque but less speed.
A lower gear ratio (like 1:3) gives more speed but less torque.
This is why gear ratio is so important in machinery—depending on what the system needs (more power or more speed), the gears are chosen accordingly.
How To Calculate Gear Ratio?
By Teeth Count
Count the number of teeth on both gears.
Gear Ratio = Teeth on Driven Gear ÷ Teeth on Driver Gear
By RPM
Measure the speed (in RPM) of both gears.
Gear Ratio = RPM of Driver Gear ÷ RPM of Driven Gear
Example:
Driver Gear: 100 RPM
Driven Gear: 25 RPM
Gear Ratio = 100 ÷ 25 = 4:1
Common Types of Gear Ratios
1:1 Ratio – Both gears rotate at the same speed (used when speed and torque remain constant).
Reduction Ratio (>1:1) – Increases torque, reduces speed.
Overdrive Ratio (<1:1) – Increases speed, reduces torque.
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