Volts to Watts Calculator
Convert volts to watts, or watts to volts, using the current. Power equals voltage times current (watts = volts × amps), so you need the amps too. Set DC, single-phase, or three-phase, and WattSimple also shows the NEC breaker and copper wire the current calls for.
Power
1,200 W
- Voltage
- 120 V
- Current
- 10 A
- Power
- 1,200 W
NEC wire & breaker for this load
- Breaker
- 15 A
- Min. copper wire (75°C)
- 14 AWG
Copper, 75°C terminations, NEC Table 310.16. Real installs may need derating for ambient heat, conduit fill, or voltage drop. Full wire & breaker chart. Always confirm with a licensed electrician + local AHJ.
Measure the real amps and volts
The converter works from nameplate or assumed figures. A clamp meter reads the actual current on one conductor without breaking the circuit; clamped around a whole cord it reads close to zero. A multimeter reads the voltage at the receptacle or terminals. Opening a panel or a live box is work for someone qualified.
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Clamp meter
Fluke 323
Best for: Measuring what a hardwired circuit actually draws, even in a crowded panel
Multimeter
Fluke 117
Best for: Anyone who will do this more than once a year
Frequently asked questions
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Sources & standards
This tool's methodology and data follow US standards and authoritative public datasets: