Watts (W)
The watt is the SI unit of power: one joule of energy per second.
Convert watts to any power unit
1 watt = 0.001 kilowatts
Quick facts
- Unit
- Watt (plural: watts)
- Symbol
- W
- Measures
- Power
- System
- Metric (SI)
- Definition
- One joule per second.
- Also written
- joule per second, J/s
1 watt in other units
| Kilowatts | 0.001 kW |
| Horsepower | 0.00134102209 hp |
| BTUs per hour | 3.412141633 BTU/h |
| Megawatts | 0.000001 MW |
| Metric horsepower | 0.001359621617 PS |
| Tons of refrigeration | 0.000284345136 TR |
| Gigawatts | 1 × 10-9 GW |
| Milliwatts | 1,000 mW |
What is a watt?
The watt is the SI unit of power: one joule of energy per second. It is used for everything from light bulbs and phone chargers to power plants, and in electricity one watt is one volt times one ampere.
A resting adult produces about 100 W of heat, and a fit cyclist can sustain 200–300 W for an hour.
Where the watt sits among power units
The watt is number 8 of 32 on our scale of power units, ordered from smallest to largest.
What watts are used for
- Appliance and bulb ratings
- Audio amplifiers and speakers
- Solar panels (peak watts)
- Cycling power meters
Watts in real life
- An LED bulb uses about 9 W
- A laptop charger delivers 45–100 W
- A person at rest produces about 100 W of heat
- A microwave oven uses about 1,000 W
Top watt conversions
Common amounts of watts
- 0.1 W
- 0.2 W
- 0.3 W
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- 2,000 W
- 2,500 W
- 3,000 W
- 4,000 W
- 5,000 W
- 10,000 W
Convert watts to all 31 other units
Metric (SI)
Horsepower
Heat & refrigeration
Mechanical & other
Convert to watts
Frequently asked questions
What is a watt?
The watt is the SI unit of power: one joule of energy per second.
How is the watt defined?
One joule per second.
How many kilowatts are in a watt?
One watt equals 0.001 kilowatts.
How many horsepower are in a watt?
One watt equals 0.00134102209 horsepower.
How many BTUs per hour are in a watt?
One watt equals 3.412141633 BTUs per hour.