Watts to Joules Calculator
Convert watts to joules by multiplying power by time in seconds: E = P × t. Find the energy used by a device, and convert it to Wh, kWh or kcal.
W
seconds
ENERGY
60,000 J
IN kJ
60 kJ
FORMULA
J = W × s
IN kWh
0.0167 kWh
💡 How to Convert Watts to Joules
To convert watts to joules, multiply the power in watts by the time in seconds. A watt is one joule per second, so a 100 W device running for 10 seconds uses 1,000 J. Watts measure a rate; joules measure the total energy, so a time is always required.
Watts to joules formula
E = P × t
E = energy in joules, P = power in watts, t = time in seconds
Example: 1,000 W × 60 s = 60,000 J (60 kJ)
E = energy in joules, P = power in watts, t = time in seconds
Example: 1,000 W × 60 s = 60,000 J (60 kJ)
Worked examples
- Microwave: 1,000 W for 2 minutes (120 s) = 120,000 J.
- LED bulb: 10 W for 1 hour (3,600 s) = 36,000 J, which is 10 Wh.
- Kettle: 3,000 W for 5 minutes (300 s) = 900,000 J (0.9 MJ, or 0.25 kWh).
Watts to joules table
| Power (W) | Time (s) | Energy (J) | Energy (Wh) | Energy (kcal) |
|---|---|---|---|---|
| 1 | 1 | 1 | 0 | 0 |
| 10 | 3,600 | 36,000 | 10 | 8.6 |
| 60 | 60 | 3,600 | 1 | 0.9 |
| 100 | 3,600 | 360,000 | 100 | 86 |
| 700 | 120 | 84,000 | 23.333 | 20.1 |
| 1,000 | 60 | 60,000 | 16.667 | 14.3 |
| 1,000 | 3,600 | 3,600,000 | 1,000 | 860.4 |
| 1,500 | 180 | 270,000 | 75 | 64.5 |
| 2,000 | 600 | 1,200,000 | 333.333 | 286.8 |
| 3,000 | 300 | 900,000 | 250 | 215.1 |
The units behind the formula
- Joule (J): the SI unit of energy. 1 J = 1 watt for 1 second = 1 volt × 1 coulomb.
- Volt (V): electric potential difference, defined as 1 joule of energy per coulomb of charge.
- Coulomb (C): electric charge. One coulomb is the charge carried by a current of 1 ampere in 1 second, about 6.242 × 1018 electrons.
- Watt (W): power, the rate of energy transfer. 1 W = 1 J per second.
Useful energy equivalents
- 1 Wh = 3,600 J (1 watt for 1 hour).
- 1 kWh = 3,600,000 J = 3.6 MJ, the unit on electricity bills.
- 1 kilocalorie (food Calorie) = 4,184 J.
- Time conversions: 1 minute = 60 s, 1 hour = 3,600 s, 1 day = 86,400 s.
Related conversions: joules to watts · watts to kWh · volts to joules
Joules = watts × seconds. 1,000 W for 60 seconds = 60,000 J. 1 kWh = 3.6 million joules.