What is a watts to joules calculator?
A watts to joules calculator turns a power rating and the length of time it is applied into the total energy delivered. A watt (W) measures how quickly energy is transferred at any instant, while a joule (J) measures the total amount of energy. Because one watt is defined as one joule per second, multiplying power by the number of seconds it runs gives the energy in joules directly.
Formula
Energy in joules equals power in watts multiplied by time in seconds:
Here is the power in watts and is the time in seconds. The result is the energy in joules.
How does it work?
- Enter the power in watts.
- Enter the time in seconds.
- Read the energy in joules. The result appears automatically once both fields are filled.
Because the relationship is a simple product, doubling either the power or the time doubles the energy delivered.
Worked examples
A 60 W light bulb left on for 10 seconds delivers:
A 100 W appliance running for 60 seconds (one minute) delivers:
Practical notes
Joules are the SI unit of energy, so this conversion is useful whenever you need a raw energy figure rather than a billing-friendly unit like the kilowatt-hour. To express a large number of joules over long periods more conveniently, divide by 3,600,000 to get kilowatt-hours, or use the watts to kWh calculator.
FAQ
How many joules are in one watt-second? Exactly one. A watt is defined as one joule per second, so a power of one watt sustained for one second delivers one joule of energy.
What if my time is in minutes or hours? Convert it to seconds first: multiply minutes by 60, or multiply hours by 3600, before entering the value here.
How do watts relate to electrical current? Power in watts also depends on voltage and current. If you need the current an appliance draws, the watts to amps calculator handles that, and the kWh to watts calculator works the other way from energy back to power.