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
The factors in use
Everything passes through watts. The tool uses 1,000 W per kW, 745.6998715822702 W per mechanical horsepower, 735.49875 W per metric horsepower (PS), 0.29307107 W per BTU per hour and 1.3558179483314003 W per foot-pound per second. Results update as you type, show up to six decimals, and use your browser's digit grouping. The default is 100 hp in kW.
Worked examples
- 100 hp = 74.569987 kW.
- 100 PS = 73.549875 kW, so 100 metric horsepower is less than 100 mechanical horsepower. Converting 100 hp the other way gives 101.386967 PS.
- 150 PS = 147.948011 hp.
- 12,000 BTU per hour = 3.516853 kW.
- 1 kW = 1.341022 hp, and 3 kW = 10,236.424905 BTU per hour.
- 550 foot-pounds per second = 1 hp, which matches the definition of mechanical horsepower.
What is and is not covered
BTU per hour here is a rate of power. The plain BTU, an amount of energy, is in the Energy Converter, so do not mix the two. Apparent power (kVA), decibel units and cooling "tons" are not offered. Negative and decimal values are accepted, and an empty box gives a prompt to enter a value.
Everyday power conversions
100 mechanical horsepower is 74.569987 kW, one kilowatt is 3,412.141635 BTU per hour, and 750 W is 1.005767 mechanical horsepower.
Mechanical horsepower (hp) and metric horsepower (PS) are different units: one PS is 0.98632 hp, so a 150 PS engine is a little under 148 hp. Check which one a car or motor rating uses before you compare two figures, because brochures in different markets use different ones.
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.
Why do 100 hp and 100 PS give different kilowatts?
They are two different units. 100 mechanical horsepower is 74.569987 kW, while 100 metric horsepower is 73.549875 kW.
How many BTU per hour is a 3 kW heater?
Select kilowatts as the source and BTU per hour as the target. 3 kW comes out as 10,236.424905 BTU per hour.
Is BTU per hour the same as BTU?
No. BTU per hour measures power. BTU alone measures energy and is converted in the Energy Converter.