The formula
hp = kW × 1.34102209
Where the factor comes from — each unit by its definition, then its size in SI:
1 kW = 1000 × W = 1,000 W1 hp = 550 × ft·lbf / s = 745.699871582 W
Dividing the two SI sizes gives the factor: 1.3410220896 (rounded for display; the underlying ratio is fixed by the definitions). The reverse factor is 0.745699871582.
Power is energy per second; the watt is one joule per second. Engine ratings in horsepower and air-conditioner ratings in BTU/h convert to watts with fixed factors.
Worked examples
- A small car engine: 74.57 kW = 100 hp — 74.57 × 1.34102209 = 100
- An old incandescent bulb (60 W): 0.06 kW = 0.0804613 hp — 0.06 × 1.34102209 = 0.0804613
- An electric kettle: 2 kW = 2.68204 hp — 2 × 1.34102209 = 2.68204
- A room air conditioner (12000 BTU/h): 3.51685 kW = 4.71618 hp — 3.51685 × 1.34102209 = 4.71618
Frequently asked questions
How many horsepower (mechanical) is 1 kW?
1 kW = 1.3410220896 hp.
How do I convert horsepower (mechanical) back to kilowatts?
Divide by 1.3410220896 — or multiply by 0.745699871582: 1 hp = 0.745699871582 kW.