The Slot Car Calculator

How fast is my slot car? How many RPM will my motor have at 10 volts?

With this slot car calculator, you can see how speed is affected by adjusting voltage, gear ratio, and wheel diameter.

The theoretical top speed is a calculated value that ignores the fact that the motor has to move the weight (mass) of the slot car and drag from the guide, axles, and gears, so the real speed is lower.

The drop-down motor list is a work in progress, where motors will be added. The RPM used in the list is an average of test results where I compare my own testing (using an optical RPM tester) with the thorough tests performed by Robert Livingstone that are published on Slot Car News: Slot Car News Motor List.

If you have your own test results or want to use the manufacturer’s rated RPM, just type in the rated RPM at 12 volts. If you only have the rated RPM at other voltages, such as 14.8v, use this formula to find the rated RPM at 12 volts: RATED RPM / RATED VOLTAGE * 12.