Gear Ratio Calculator
Work out gear ratio instantly with clear inputs, formula shown and shareable results.
About Gear Ratio Calculator
Gear ratio is driven teeth over driver teeth. A 20-tooth gear driving a 60-tooth gear is a 3:1 reduction, so output speed is a third of input while torque triples - power is conserved apart from mesh losses. Ratios below one are overdrives, trading torque for speed.
Formulas
Gear ratio
ratio = driven teeth / driver teeth
Speed and torque
output rpm = input rpm / ratio; output torque = input torque x ratio
Worked example
With the default values below, Gear Ratio Calculator returns Gear Ratio of 3.0000. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Teeth on the driving gearminimum 1
- 20
- Teeth on the driven gearminimum 1
- 60
- Input speedminimum 0 rpm
- 1,800 rpm
- Input torqueminimum 0 N m
- 25 N m
Results
- Gear Ratio
- 3.0000
- Output Speed
- 600.0 rpm
- Output Torque
- 75.000 N m
- Expressed As
- 3:1 reduction
Step by step
- 1Values used
- 2Gear ratio
- 3Speed and torque
- 4Gear Ratio= 3.0000
- 5Output Speed= 600.0 rpm
- 6Output Torque= 75.000 N m
- 7Expressed As= 3:1 reduction
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
Why does torque rise when speed falls?
Because power is torque times angular speed and gears do not create power. Cutting speed threefold must triple torque to keep the product the same.
Does the module or pitch matter?
Not for the ratio - only tooth counts do. Pitch has to match between meshing gears for them to run at all, though.