How this calculation works
For a DC circuit, power in watts is voltage in volts multiplied by current in amperes. AC real power needs additional information such as power factor and phase configuration.
Power = voltage × currentA worked example
12 V at 2 A corresponds to 24 W.
Good to know
Assumes the idealized model described above. Use consistent units and independently verify figures before a consequential decision.
Power is a rate, while energy accumulates over time
A 24 W load operating at that constant power for two hours uses 48 watt-hours of energy. Watts and watt-hours answer different questions: the first describes a rate, the second an accumulated amount.
Voltage times current gives watts in this DC model. It does not by itself tell you battery runtime, because runtime also depends on usable stored energy, efficiency and how the load changes.
An AC nameplate can need more information
For AC systems, simply multiplying RMS voltage and current can give apparent power rather than real power. Power factor, waveform and phase configuration matter. This calculator is explicitly scoped to the DC relationship.
Use volts and amperes. Convert milliamps, kilovolts or other prefixes before entering the values, and do not interpret a calculated power as an installation safety assessment.
A few questions, answered
Does the answer represent energy usage?
No. It is power in watts. Energy requires multiplying power by an appropriate duration.
Can this calculate real three-phase AC power?
No. It does not include phase configuration or power factor.