Joules to Watts Calculator
Enter energy in joules and the time in seconds — the watts update instantly.
How do you convert joules to watts?
Divide joules by the time in seconds: W = J ÷ s. A kettle using 30,000 J over 10 s delivers 30,000 ÷ 10 = 3,000 W. One watt equals one joule per second, so power is the rate at which energy is used — the same energy over a shorter time means more watts.
Joules to Watts Formula
A joule is a unit of energy; a watt is a unit of power, defined as one joule per second (1 W = 1 J/s). To get power, divide the total energy by the time over which it is delivered. Energy and power are not interchangeable — you always need the time to move between them.
Joules to Watts Over Common Time Periods
| Energy | over 1 s | over 10 s | over 60 s |
|---|---|---|---|
| 100 J | 100 W | 10 W | 1.67 W |
| 1,000 J | 1,000 W | 100 W | 16.7 W |
| 3,600 J | 3,600 W | 360 W | 60 W |
| 10,000 J | 10,000 W | 1,000 W | 167 W |
| 30,000 J | 30,000 W | 3,000 W | 500 W |
Frequently Asked Questions
How do I convert joules to watts?
Divide joules by the time in seconds: W = J ÷ s. For example, 30,000 J over 10 s is 30,000 ÷ 10 = 3,000 W. One watt equals one joule per second.
Do I need the time to convert joules to watts?
Yes. Joules measure energy and watts measure power (energy per second). Without the time, there is no way to find the wattage — it is a required input.
How many watts is 3,600 joules?
It depends on the time. 3,600 J over 1 s = 3,600 W; over 60 s = 60 W; over one hour = 1 W. (3,600 J is also exactly 1 watt-hour.)
What is the difference between joules and watts?
A joule is a fixed quantity of energy; a watt is a rate — one joule per second. Using 100 J in 1 s draws 100 W, but the same 100 J over 100 s is just 1 W.