Vehicle Road Speed Calculator

This is a JavaScript page that lets you calculate the roadspeed of your vehicle.

Sorry, but without JavaScript enabled, you won’t be able to use this calculator.

You will need to enter the following data:

  1. Motor speed, at the full battery voltage you intend to use. This is usually the name plate rating of the motor, but if you are using the motor at a higher voltage than its name plate rating, increase the name plate speed in proportion. So if the motor is a 24v motor, rated at 3000 rpm, you will need to enter 4500 rpm as the motor speed.
  2. Drive gear ratio. This is the shaft reduction speed ratio between the motor shaft and the output shaft. If, for instance, you are using a chain drive and there are 10 teeth on the motor sprocket and 80 teeth on the wheel sprocket, then the gear ratio would be 8.
  3. Road wheel diameter. This is the actual diameter of the wheel, that is in contact with the road. You can measure the diameter in millimetres, centimetres or inches, but you will need to tell the calculator which.

When you’ve entered all these figures, click on the Calculate button and the calculator will show your speed in Km/Hr and in Miles/Hr.

If you’ve entered any parameter and the calculator can’t make it a number, you will get an error message NaN.
If you get a result 0 or Infinity – you’ve left an input blank.

What is the motor RPM at full battery voltage?
What is the overall reduction gear ratio?
What is the road wheel diameter?

Select whether this is Centimetres, Millimeters or Inches.

Your Road Speed is: Km per Hour
Which is: Miles per Hour

There is also a motor current calculator.