💡 Watt Calculator
Calculate electrical power in watts from any two of voltage, current, and resistance.
What does this calculator do?
Electrical power in watts describes the rate at which electrical energy is converted into work, heat, or light. This calculator finds power from whichever two of voltage, current, and resistance you know, using the fundamental relationships between them.
How this calculator works
Depending on your inputs, the calculator applies one of the standard power formulas: P = V × I (voltage times current), P = I² × R (current squared times resistance), or P = V² / R (voltage squared divided by resistance). These all come from combining Ohm’s Law (V = I × R) with the basic power definition, and they give the same answer for a given circuit.
This tool is for general electrical education and estimation. For circuit design or safety-critical work, verify calculations with a qualified electrician or engineer.