Ohm's Law Calculator

Enter any two of voltage, current, resistance or power and get the other two. V = I × R, P = V × I.

Enter any two values, then the other two are filled in automatically.

Voltage
Current
Resistance
Power

Frequently asked questions

What is Ohm's law?

It states that voltage equals current times resistance: V = I × R. Combined with power P = V × I, any two of the four quantities determine the other two.

Which two values should I enter?

Any two — voltage and current, current and resistance, power and voltage, and so on. The calculator detects the pair and derives the rest.

What units does it use?

Volts (V), amperes (A), ohms (Ω) and watts (W) — the standard SI electrical units.