Power converters
6 conversions between 5 power units. Every page includes a live converter, the formula and a full conversion table.
Units covered
| Unit | Symbol | In watts |
|---|---|---|
| Watt | W | 1 |
| Kilowatt | kW | 1,000 |
| Megawatt | MW | 1,000,000 |
| Horsepower | hp | 745.699872 |
| BTU per hour | BTU/h | 0.2930711 |
All power conversions
- Watts to Kilowatts
- Watts to Horsepower
- Kilowatts to Watts
- Kilowatts to Horsepower
- Horsepower to Watts
- Horsepower to Kilowatts
Power is a rate, energy is an amount
A watt is one joule per second — a rate of delivery, not a quantity. The distinction matters when reading a specification: a kettle rated at 3 kW draws that much while it is on, and how much energy it uses depends entirely on how long you run it. Multiply the rate by the time and you get energy, which is why your electricity bill is in kilowatt-hours rather than kilowatts.
Three different horsepower
The unit is not standardised. Mechanical horsepower, the one meant in English-speaking car specifications, is 745.7 W. Metric horsepower — PS in German, CV in French and Italian — is 735.5 W, about 1.4% smaller, and is what European manufacturers quote at home. A car advertised as 300 PS is 296 hp, which is where small discrepancies between a manufacturer's figures in different markets usually come from. This site uses mechanical horsepower.
James Watt derived the unit by measuring how much a working horse could lift, specifically to sell steam engines against the animals they replaced. A real horse can exceed one horsepower briefly and sustains rather less.
BTU per hour
Heating and air conditioning in the US are rated in BTU per hour, which is a power despite looking like an energy unit — the "per hour" is doing the work. One watt is about 3.41 BTU/h, so a 12,000 BTU/h air conditioner is roughly 3.5 kW of cooling. Confusingly, that same machine is often called a "one ton" unit, from the rate of cooling one ton of ice melting over a day.