Ohm's Law Calculator

Formula

How this is calculated

Ohm's law links the three core electrical quantities of a circuit: voltage (V, in volts), the potential difference pushing charge; current (I, in amperes), the rate of charge flow; and resistance (R, in ohms), how strongly the conductor opposes that flow. The single relationship V = I × R ties them together, so knowing any two lets you solve for the third by rearranging it to I = V ÷ R or R = V ÷ I.

This calculator reads whichever two fields you fill in, then derives the missing value. It also computes electrical power from P = V × I (watts), the rate at which energy is dissipated, typically as heat in resistive elements.

The math assumes an ideal ohmic component at steady state, where resistance is constant and independent of voltage or temperature, and it covers only direct current (DC). Real parts drift with heat, and non-ohmic devices like diodes break the linear rule. Dividing by a zero current or zero resistance is undefined, so those cases return no result.