kW to km/h Calculator
Estimate an electric vehicle's speed in km/h from motor power and weight.
This calculator estimates a vehicle's speed in km/h from its motor power in kilowatts and its weight — handy for electric vehicles, which are usually rated in kW rather than horsepower.
How It Works
Electric motors are rated in kilowatts, so this tool converts to horsepower first, then applies the same power-to-weight speed estimate used for combustion cars. Real EV top speed is often electronically limited below this figure for efficiency and range.
How to Use This Calculator
- Enter motor power in kW.
- Enter weight in kilograms.
- Read estimated speed in km/h and MPH.
Worked Example
Why EVs Are Rated in kW
Electric vehicles quote motor output in kilowatts because it maps directly to the battery and charging system, both measured in kW and kWh. To compare an EV against a petrol car's horsepower, convert kW to HP (×1.341) first. This calculator does that automatically, then estimates achievable speed from the resulting power-to-weight ratio.
Why Real EV Top Speed Is Often Lower
Most EVs are electronically limited well below their theoretical power-derived speed. Manufacturers cap top speed to protect range (drag rises with the cube of speed, draining the battery fast), to stay within tire and motor thermal limits, and for stability. So treat this figure as a performance-potential estimate, not a number the car will actually reach unrestricted.
Estimated Speed by Power (1,800 kg EV)
| Motor Power | Approx. HP | Est. Speed |
|---|---|---|
| 100 kW | 134 | ~160 km/h |
| 150 kW | 201 | ~185 km/h |
| 250 kW | 335 | ~220 km/h |
Frequently Asked Questions
Convert kilowatts to horsepower (×1.341), then estimate speed from the power-to-weight ratio. The calculator does both steps automatically.
Kilowatt is the SI unit for power and is standard for electric motors worldwide. Many makers also quote the horsepower equivalent for familiarity.
Not necessarily. Many EVs are electronically limited below their theoretical maximum to protect range, motor, and tires.
About 201 mechanical horsepower, since 1 kW equals roughly 1.341 HP.
Through power-to-weight, yes, especially in acceleration. At high speed, aerodynamic drag becomes the dominant factor.