Ohm's Law Calculator

Ohm's Law states that the voltage across a conductor is directly proportional to the current flowing through it, with resistance being the constant of proportionality. The formula is V = I x R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms.

Select the 'Resistance' mode, enter the voltage and current values, and the calculator instantly computes R = V / I. For example, 12V with 0.5A gives a resistance of 24 ohms.

Power dissipation is the amount of electrical energy converted to heat, measured in watts (W). It is calculated using P = V x I. This calculator automatically computes power dissipation and warns you if it exceeds 0.25W, which is the rating of a standard quarter-watt resistor.

Ohm's Law can be rearranged in three ways: V = I x R (to find voltage), I = V / R (to find current), and R = V / I (to find resistance). This calculator supports all three modes — just select which value you want to calculate.

Ohm's Law applies directly to DC circuits. For AC circuits, the concept extends to impedance (Z), which includes resistance, capacitive reactance, and inductive reactance. For pure resistive AC loads, Ohm's Law works the same way using RMS voltage and current values.