Power Converter
Convert between watts, kilowatts, horsepower, BTU per hour, and foot-pounds per second.
How power conversion works
Every power unit here converts through the watt — the SI base unit of power, defined as one joule of energy transferred per second. Horsepower predates the watt and was originally defined by James Watt himself to compare steam engines against actual horses, which is why it's not a round number of watts.
Common conversions
- 1 horsepower (mechanical) ≈ 745.7 watts ≈ 0.7457 kW
- 1 metric horsepower (PS) ≈ 735.5 watts — slightly less than mechanical horsepower
- A typical car engine might be rated around 100–300 horsepower (75–225 kW)
- 1 kilowatt = 1,000 watts, roughly 1.34 horsepower
Frequently asked questions
Why are there two kinds of horsepower?
Mechanical (imperial) horsepower, used mainly in the US and UK, is defined as 550 foot-pounds per second. Metric horsepower (PS, from the German Pferdestärke), used in much of Europe and Asia for car specifications, is defined slightly differently at 75 kilogram-force-meters per second — about 1.4% less than mechanical horsepower.
What's BTU per hour used for?
It's the standard unit for rating air conditioners, furnaces, and heaters in the US — a 12,000 BTU/hr air conditioner is a common '1-ton' unit size for a small room.