How to use the Gear Ratio Calculator

Find gear reduction ratio and driven shaft RPM from gear tooth counts.

Calculation formula

Gear ratio = driven gear teeth ÷ driving gear teeth; output RPM = input RPM ÷ ratio for a simple external gear pair.

Recommended steps

1. Enter values using the units shown beside each field.
2. Review whether the example assumptions match your situation.
3. Run the calculator and compare the key metrics.
4. Use the source data or official rates when precision matters.

Known limitations

Assumes a simple single-stage gear pair with negligible slippage; rotation direction is reversed and efficiency is not considered.