Gear Tooth Ratio Calculator

Inputs

View results
Teeth on the stage 1 driving (input) gear.
Teeth on the stage 1 driven (output) gear.
0 for a single stage.
Teeth on the stage 2 driven gear. 0 for a single stage.
Speed of the stage 1 driving gear.
rpm

Results

Default result
Edit inputs
Total ratio(i)
3
Pass

3.00:1 reduction (output slower)

Stage 1 × stage 2 (n:1).

Also computed

Stage 1 ratio(i₁)3

z₂ ÷ z₁.

Stage 2 ratio(i₂)1

z₄ ÷ z₃ (1 if single stage).

Output speed(n₂)500rpm

Method notes 4 notes
  • Each stage ratio is driven teeth ÷ driving teeth; the stages multiply for the total compound ratio.
  • Single stage: leave the stage 2 teeth at 0.
  • An idler gear between two gears changes the direction of rotation only — it does not change the ratio.
  • Ratios are unit-independent and assume external spur meshes (each stage reverses rotation); efficiency losses are ignored.

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