About this tool
Enter any two of voltage, current, resistance and power, and the other two are computed live using Ohm's law (V=IR) and the power law (P=VI). Everything runs locally in your browser.
Frequently asked questions
Which values do I need to enter?
Any two of the four. From two known quantities the calculator derives the remaining two using V = I × R and P = V × I.
What units are used?
Voltage is in volts (V), current in amperes (A), resistance in ohms (Ω) and power in watts (W).