12 Watts to Joules
Watts measure power and joules measure energy, so the answer depends on time. Here is what a 12 W device uses over each period.
12 J per second
Because 1 watt = 1 joule per second, 12 W delivers 12 J every second it runs.
- Per minute
- 720 J
- Per hour
- 43,200 J
- Per hour (kWh)
- 0.012 kWh
- Per day
- 1,036,800 J
12 watts to joules, explained
A watt is a rate: one watt means one joule of energy is used every second. So 12 watts means 12 joules per second. To get a total number of joules you multiply by how long the power runs.
For example, a 12 W device left on for one hour uses 12 × 3,600 = 43,200 J. Over a full day it uses 1,036,800 J. On an electricity bill, one hour of use is 0.012 kWh.
12 W draws about 20% of the power of an old-style 60 W incandescent bulb. One hour at 12 W consumes 0.012 kWh of electricity — about 0.18¢ at a US average residential rate of $0.15 per kWh.
joules = 12 W × time in secondsTablet charger (12 W)
Medium-sized tablets consume around 12 watts from the outlet during charging cycles.
Electrical Power Comparison Scale
Need a different power or time? Use the interactive converter below for any combination.
12 W energy over time
| Time on | Energy (joules) |
|---|---|
| 1 second | 12 J |
| 1 minute | 720 J |
| 10 minutes | 7,200 J |
| 1 hour | 43,200 J |
| 6 hours | 259,200 J |
| 1 day | 1,036,800 J |
Convert any wattage and time
The full Watts to Joules converter handles W, kW, MW, any time unit, and the reverse joules→watts and time calculations.
FAQ: 12 watts
How many joules is 12 watts?
12 watts is not a fixed number of joules on its own — watts measure power and joules measure energy, so you need a time. A 12 W device uses 12 J every second, 43,200 J over one hour (0.012 kWh).
How do you convert 12 watts to joules?
Multiply 12 by the number of seconds the power runs. Joules = 12 × time in seconds. For one hour that is 12 × 3,600 = 43,200 J.
How much energy does a 12 W device use per hour?
A 12 W device running for one hour uses 43,200 J, which is 0.012 kWh on an electricity bill.