Top Speed Estimator
Estimate a device's theoretical top speed from wheel diameter and motor RPM — or derive RPM from the motor's kV and pack voltage.
Theoretical top speed
Speed is π × wheel diameter × RPM. This is the theoretical no-load figure — real top speed is lower once you add rider drag, tyre squash, controller speed limits, and the RPM the motor loses under load.
Wheel size, motor speed, and the number on the spec sheet
Speed on a wheeled device comes down to two things: how far you travel per wheel revolution, and how many revolutions happen each minute. The first is pure geometry — the wheel's circumference. The second is the motor's RPM, which you either know directly or can estimate from the motor's kV rating and the voltage feeding it.
Put them together and you have a clean theoretical top speed. Treat it as a ceiling rather than a promise: real riding adds drag, load, tyre deflection, and electronic speed limits, all of which pull the achievable number down from the calculated one.
Frequently Asked Questions
How is top speed calculated from wheel size and RPM?
One wheel revolution moves the board forward by its circumference — pi times the wheel diameter. Multiply that by the motor's revolutions per minute and you get distance covered per minute, which converts directly to km/h and mph. So speed = pi × diameter × RPM, all in consistent units.
What is motor kV and how does it give me RPM?
A motor's kV rating is its speed constant — the no-load revolutions per minute it turns for each volt applied. Multiply kV by your pack voltage to get the approximate no-load RPM. For example, a 12 kV motor on a 36V pack spins around 432 RPM with no load, which you can then feed into the speed formula.
Why is this a 'theoretical' top speed?
The formula gives the no-load figure — the speed the wheel would reach if nothing resisted it. In reality the motor loses RPM under the load of moving a rider, the tyre squashes slightly (reducing effective diameter), air resistance grows with speed, and most devices have a firmware speed limiter. Actual top speed is typically noticeably lower than the calculated value.
Does a bigger wheel make the device faster?
At the same RPM, yes — a larger wheel covers more ground per turn, so it's faster. That's part of why large-wheel electric unicycles and scooters reach higher speeds than small hoverboard wheels. But wheel size interacts with motor torque and gearing, so it isn't the only factor, and a bigger wheel can accelerate more slowly.
Should I ride at my device's top speed?
Top speed is a specification, not a recommendation. Handling, braking distance, and the consequences of a fall all get worse as speed rises, and small obstacles become far more dangerous. Ride well within your device's and your own limits, wear protective gear, and slow down in traffic, on rough surfaces, and around people.
Estimates only — real top speed is lower and varies with load, tyre, and firmware limits. Ride safely, wear a helmet, and follow your local law.