Kilowatts to horsepower (mechanical) – and horsepower (mechanical) to kilowatts

Formula

Multiply the value in kilowatts by 1.3410221 to get horsepower (mechanical).
hp = kW × 1.3410221

Multiply the value in horsepower (mechanical) by 0.74569987 to get kilowatts.
kW = hp × 0.74569987

How to convert kilowatts to horsepower (mechanical)

Type a value in the field above and the result is calculated instantly. Use the arrow button to swap direction, or pick other units from the lists.

Doing it in your head

A rough conversion for when the calculator is not to hand. The error comes last, and it holds in both directions at that order of magnitude.

• Kilowatts to horsepower (mechanical): × 3 ÷ 2 − 10%. That gives 1.35 instead of 1.34102, an error of 0.67%.
• Horsepower (mechanical) to kilowatts: × 3 ÷ 4. That gives 0.75 instead of 0.7457, an error of 0.58%.

About the units

Kilowatts. A kilowatt is 1,000 watts and the legal unit of power for vehicles in the EU: the type-approval information document requires engine power in kilowatts. Chargers, heat pumps and solar installations are rated in kilowatts too. One kilowatt is 1.341 mechanical horsepower, 1.360 metric, and about 3,412 Btu per hour. Two traps. The kilowatt is power and the kilowatt-hour energy – one kilowatt for one hour is exactly one kilowatt-hour. And a 150 kW car is a little over 200 horsepower, depending on the variant.

Horsepower (mechanical). Horsepower comes in several variants. This conversion uses the mechanical one, defined as 550 foot pounds-force per second, which makes it 745.69987158227 watts. Metric horsepower – Swedish hk, German PS – is 75 kilogram-force metres per second, 735.49875 watts, and electric horsepower is exactly 746 watts. Horsepower is absent from the EU units directive and may appear only as a supplementary indication beside the kilowatt figure. The trap is therefore the number itself: 150 PS is 110.3 kW, while 150 hp is 111.9.