⚡ Watts / Volts / Amps Calculator
Enter any two values and Ohm's Law fills in the other two — power, voltage, current and resistance.
About this calculator
Watts, volts and amps are different quantities, not interchangeable units — you can't convert one directly without a second known value. They are tied together by Ohm's Law and the power equation: power equals voltage times current (P = V × I), and voltage equals current times resistance (V = I × R). Give this tool any two of the four values and it solves the rest.
Handy for sizing a power supply, picking a fuse or wire gauge, checking an LED resistor, working out how many amps an appliance draws from its wattage, or any basic DC / resistive electronics question. For AC loads with a power factor (motors, transformers), see the note below the results.