Electric Power Calculator

Calculate ideal DC electrical power in watts and one-hour energy in watt-hours from voltage and current.

Calculate DC electrical power

Power: 36 WEnergy per hour: 36 Wh

How this tool works

Electrical power measures energy transfer rate. This calculator applies the ideal direct-current relationship and reports the equivalent energy used during one constant hour, keeping power and energy units distinct.

For an ideal DC circuit, power P equals voltage V multiplied by current I. Maintaining that constant power for one hour consumes the same numeric quantity in watt-hours.

How to use it

  1. Enter voltage in volts.
  2. Enter current in amperes.
  3. Read instantaneous power and the one-hour energy equivalent.

Worked examples

DC accessory

Input
12 V and 3 A
Output
36 W

Multiplying twelve volts by three amperes gives a power transfer rate of 36 joules per second, or 36 watts.

USB example

Input
5 V and 2 A
Output
10 W

Five volts multiplied by two amperes gives ten watts and would equal ten watt-hours if held constant for one hour.

Limitations

  • AC power can require power factor and phase information.
  • Actual devices may vary current and incur conversion losses.