Speed Converter
Convert between km/h, mph, and m/s — and turn wheel RPM into road speed for any wheel diameter.
Converted speed
A wheel covers one circumference (π × diameter) per revolution, so road speed follows directly from RPM and wheel size. Conversions use 1 m/s = 3.6 km/h = 2.237 mph.
One speed, three ways of writing it
Device specs, local speed limits, and rider communities don't agree on units — a scooter rated in mph, a bike lane posted in km/h, and a physics rule of thumb in m/s all describe the same motion. Converting between them cleanly means you can compare a device's quoted top speed against a local limit without second-guessing the arithmetic.
The second panel closes the loop back to hardware: given a wheel's diameter and how fast it spins, it works out the actual road speed, which is useful for sanity-checking a motor's numbers or understanding why a bigger wheel travels further per turn.
Frequently Asked Questions
How do I convert km/h to mph?
One kilometre per hour is about 0.6214 miles per hour, so multiply km/h by 0.6214 to get mph, or divide mph by that to go the other way. For example, 25 km/h is roughly 15.5 mph. This converter does it both ways and also shows metres per second.
Why does m/s matter for personal transport?
Metres per second is the physics-native unit, and it's handy when you're reasoning about stopping distance or the energy of a fall, both of which scale with speed. It also links cleanly to wheel RPM: road speed in m/s is the wheel's circumference in metres times revolutions per second.
How does wheel RPM become road speed?
Each revolution moves the device forward by one wheel circumference, which is pi times the wheel's diameter. Multiply that by revolutions per minute and divide by 60 to get metres per second, then convert to km/h or mph. Enter your wheel RPM and diameter and the tool does the arithmetic.
Are the conversions exact?
The unit conversions use standard exact factors (1 m/s = 3.6 km/h = 2.236936 mph) and round the result for display. The RPM-to-speed figure is exact for the numbers you enter, but real road speed can differ slightly because a loaded tyre's effective diameter is a little smaller than its unloaded size.
What's a sensible speed for a hoverboard or scooter?
It varies widely by device and rider — small hoverboards top out around walking-to-jogging pace, while commuter scooters and electric unicycles can go much faster. Whatever the number, faster means longer stopping distances and harder falls, so choose a speed you can control for the surface, traffic, and your own skill, and check what your local law permits.
Estimates only — a loaded tyre's effective diameter can shift the RPM-based figure slightly. Ride safely, wear a helmet, and follow your local law.