Gear Ratio Calculator
Find the tooth-count ratio and output speed for one meshing gear pair.
Formula
i = z₂/z₁; n₂ = n₁/i
Gear ratio ≈ (60)÷(20) · Output speed ≈ (900)÷(3)
How to use
- Enter the driver and driven tooth counts.
- Enter the driver speed in rpm.
- Read the reduction ratio and output speed magnitude.
Examples
- 20 teeth driving 60 teeth at 900 rpm gives 300 rpm.
Frequently asked questions
What does a ratio of 3 mean?
The output makes one turn for every three input turns.
Which direction does the output turn?
External gears turn oppositely; an internal gear pair turns in the same direction.
Does this check gear compatibility?
No. Module, pressure angle, interference and load capacity need separate checks.
Sources
Updated: