RC Gear Ratio Calculator

Calculate final drive ratio and rollout, then see how one-tooth pinion changes shift the balance between torque and top speed.

Pinion Gear Teeth

Spur Gear Teeth

Internal Ratio

Tire Diameter (mm, optional)

Final Drive Ratio

External Ratio

Internal Ratio

Rollout

Pinion Swap Chart

See how one-tooth changes affect your ratio with the same spur gear.

Pinion	Ext. Ratio	Final Ratio	Change	Effect

Lower final ratio usually means more top speed and less mechanical advantage.
Higher final ratio usually means more torque, cooler motor temps, and slower top speed.
Rollout helps compare setups across different tire diameters.
Small gearing changes can push motor and ESC temperatures hard, so recheck temps after testing.