Power Calculator
Calculate power from voltage, current, resistance or other inputs.
Power formulas
P = V × I, P = V² ÷ R, P = I² × R, and P = E ÷ t.
Power Formulas
Electrical power can be calculated from different combinations of voltage, current, resistance and energy.
P = V × I
P = V² ÷ R • P = I² × R • P = E ÷ t
How to Use the Power Calculator
1
Choose a Calculation
Choose whether to calculate power from voltage and current, voltage and resistance, current and resistance, or energy and time.
2
Enter the Known Values
Enter the two known quantities and select their units.
3
Calculate
The calculator converts the inputs and displays power in watts and kilowatts.
Example
A circuit operates at 230 V and draws 10 A.
Power = Voltage × Current.
P = 230 × 10 = 2,300 W.
Power = 2.30 kW
Frequently Asked Questions
Electrical power is the rate at which electrical energy is transferred or consumed. It is commonly measured in watts (W) or kilowatts (kW).
Multiply voltage by current: P = V × I. For example, 12 V × 2 A = 24 W.
If voltage and resistance are known, use P = V² ÷ R. If current and resistance are known, use P = I² × R.
One kilowatt equals 1,000 watts. Power ratings for larger loads are often expressed in kilowatts.