Electrical Power
Enter any two
Fill exactly two of the four values; the other two are computed live.
Result
How to use this calculator
Electrical power is the rate at which electrical energy is converted into other forms (heat, light, motion). This tool uses the full set of power–Ohm's-law relations: P = V·I, P = I²·R and P = V²/R. Enter any two of the four quantities — power P, voltage V, current I, resistance R — and it computes the other two instantly, each in the most readable unit (W, V, A, Ω).
What it means in a real circuit
Power is what your utility bills you for and what determines how hot components get. P = I²·R shows why even a small voltage drop across a high current draw wastes meaningful energy in wiring; P = V²/R is why a bulb's wattage changes with line voltage. Engineers use these relations to size power supplies, select resistors, estimate battery drain and calculate losses in motors, transformers and transmission lines.