FREE ONLINE CALCULATOR

Gear Ratio Calculator

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

✓ Instant results ✓ Editable inputs ✓ Formula explained

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AUTOMOTIVE · TOOLS

ROAD READY Practical inputs · Clear cost estimates

CALCULATION TOOL

Gear Ratio Calculator

Change any value and calculate again.

Uses the values you enter. No account required.

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HOW IT WORKS

The calculation

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

Read the full guide →

ASSUMPTIONS

Know the limitations

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

Results are estimates derived from your inputs.

ABOUT THIS TOOL

When to use a gear ratio calculator

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

All assumptions are visible and adjustable. Check rates and underlying data against original sources before making a decision.