Ohm's Law Calculator
Solve for voltage, current, resistance, or power in a simple DC circuit using Ohm's Law.
The formulas
Ohm's Law: V = I × R (voltage = current × resistance). Power: P = V × I (power = voltage × current).
Worked example
A 12V supply across a 4Ω resistor draws a current of 12 ÷ 4 = 3A, and dissipates power of 12 × 3 = 36W.
Frequently asked questions
Does this work for AC circuits?
This calculator uses the basic DC form of Ohm's Law. AC circuits with reactance (from capacitors or inductors) need impedance instead of plain resistance, which this tool doesn't model.
Why is power always shown?
Once voltage and current are known (directly or derived), power follows immediately from P = V × I, so it's included alongside every result at no extra input cost.