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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.

Convert

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.

Frequently asked questions

You can't go straight from volts to watts — you need the current too. Power = voltage × current, so watts = volts × amps for a DC or single-phase circuit. Example: 120 volts × 10 amps = 1,200 watts. For three-phase, multiply by 1.732 (√3) and the power factor.

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Sources & standards

This tool's methodology and data follow US standards and authoritative public datasets: