Ohms Law Calculator
Solve Ohms law for voltage, current, and resistance with real-time calculations and step-by-step electrical formulas.
What Is Ohm's Law?
Ohm's law relates voltage, current, and resistance in a linear electrical circuit. It is the starting point for analyzing resistors, wires, and many basic DC circuits before adding capacitors or inductors.
Ohm's Law Formula
The fundamental relationship is:
$$V = I \times R$$Solve for any one unknown when the other two are known: \(I = V/R\) or \(R = V/I\). Power dissipated in a resistor is \(P = VI = I^2 R = V^2/R\).
Related tools: Amps to Volts Calculator, LED Resistor Calculator, and HP to Amps Calculator.
Frequently Asked Questions
What units does Ohm's law use?
Voltage in volts (V), current in amperes (A), and resistance in ohms (Ω). All three must use consistent SI-derived units.
Can I use Ohm's law for AC circuits?
For resistive AC loads, the same formula applies to RMS voltage and current. Reactive components need impedance \(Z\) instead of pure resistance.
What if resistance is zero?
Zero resistance implies infinite current for any fixed voltage, which is not physical. Real wires have small but nonzero resistance.
How do I find power from Ohm's law?
Multiply voltage by current: \(P = VI\). With only \(I\) and \(R\), use \(P = I^2 R\). With \(V\) and \(R\), use \(P = V^2/R\).
Does Ohm's law apply to all materials?
It holds for ohmic conductors where current is proportional to voltage. Diodes, transistors, and arcs are non-ohmic and need different models.
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