Ohm's Law Calculator
Calculate voltage, current, resistance and power using Ohm's Law (V = IR). Enter any two values to find the other two instantly.
How to use this tool
- Enter voltage (v), current (i) and resistance (r) in the fields above.
- Results update instantly as you type — or click Calculate.
- Read your voltage and the full breakdown beneath it.
Ohm's Law states V = I × R: voltage equals current times resistance. Power is P = V × I = I²R = V²/R. Enter any two of V, I, R and the calculator finds the rest.
Frequently asked questions
- What units are used?
- Volts (V) for voltage, Amperes (A) for current, Ohms (Ω) for resistance, and Watts (W) for power. Keep units consistent.
- Does Ohm's Law apply to AC circuits?
- For pure resistors, yes. For capacitors and inductors you need impedance Z (complex resistance), and V = IZ replaces V = IR.