RC car gearing calculator



Instructions and details

Use at your own risk :-) The calculated values are not saved anywhere. Version : 0.95
Date : 2021-03-30

Gear ratio

Select pinion tooth count

Select spur gear tooth count

Calculated gear ratio:

: 1

The number reflects how many revolutions does the pinion gear make to turn the spur gear one revolution.

Transmission ratio

You can set the transmission ratio to 1:1 value, calculate the ratio based on transmission gear sizes or manually enter the ratio if it is already known. It is presumed that the transmission consists of 3 gears. The middle/idle gear doesn't have to be taken into account in calculations.
: 1

Top/input gear tooth count

Bottom/diff gear tooth count

Calculated transmission ratio:

1 : 1

Total drive reduction ratio:

1 : 1

The amount of revolutions that the pinion gear must turn in order to turn the wheels one revolution.

RPM to transmission

Motor kilovolts amount

kv Enter the kilovolts amount of the motor. The kilovolts amount indicates how many revolutions the motor will make in one minute per volts applied

LiPo Battery voltage

Battery voltage when fully charged. A nominal voltage for LiPo batteries is 3.7 v per cell.

Motor RPM value:


The motor spins this many rounds per minute.

RPM to transmission value:


The amount of revolutions that the motor and pinion and spur gear combination will cause the transmission to turn in one minute. This is the RPM value entering the transmission through spur gear, not taking transmission ratio into account.

RPM to wheels value:


The amount of revolutions that the this gearing combination will cause the driving wheels to turn in one minute.

Rollout and theoretical top speed

Tire diameter

Rollout values

Theoretical top speed


The top speed calculation is only a theoretical number with no assumptions about friction and other parameters that make the real-world top speeds significately slower.

The RC car goes meters in second


Version 0.90 (C) 2021 Pii-Atomi Tmi