Ohms Law Calculator
Calculate voltage, current, resistance
Frequently Asked Questions
What is Ohm's Law?
Ohm's Law states that voltage equals current times resistance: V = I × R. If you know any two values, you can calculate the third. For example, 12V across a 4Ω resistor produces 3A of current.
How do I calculate power using Ohm's Law?
Power (watts) can be calculated three ways: P = V × I, P = I² × R, or P = V² / R. A 12V circuit with 2A current dissipates 24 watts. The calculator shows all related values.
What is the difference between series and parallel resistance?
Series: R_total = R₁ + R₂ + R₃. Parallel: 1/R_total = 1/R₁ + 1/R₂ + 1/R₃. Two 100Ω resistors in series = 200Ω. In parallel = 50Ω. The calculator handles both configurations.
What units are used in Ohm's Law?
Voltage in volts (V), current in amperes (A), resistance in ohms (Ω), power in watts (W). Common prefixes: milliamps (mA = 0.001A), kilohms (kΩ = 1000Ω), megohms (MΩ = 1,000,000Ω).
Does Ohm's Law apply to AC circuits?
Ohm's Law applies to AC circuits using impedance (Z) instead of resistance: V = I × Z. Impedance includes resistance plus reactance from capacitors and inductors. For purely resistive AC loads, V = I × R still applies directly.