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Ohm's Law Calculator

Ohm's law links the voltage, current and resistance of a circuit: when you know two of them, you can work out the third. Enter any two values and press Calculate.

How this calculator works

The form has three number fields: Voltage, Current and Resistance. Enter the two values you know and press the Calculate button, and the tool works out the remaining one.

Results appear in cards below the button. Copy writes a result and its unit to the clipboard, and Clear resets the form. Everything runs in the browser and nothing is uploaded.

Ohm's law formula

Ohm's law relates three quantities: the voltage V in volts (V), the current I in amps (A) and the resistance R in ohms (Ω). The current is equal to the voltage divided by the resistance, I = V / R. For example, with a voltage of 5 V and a resistance of 50 Ω, the current is 0.1 A.

The same relationship can be turned around in two ways. The voltage equals the current times the resistance, V = I × R: a current of 0.1 A through a resistance of 50 Ω gives a voltage of 5 V. The resistance equals the voltage divided by the current, R = V / I: with 10 V and a current of 0.005 A, the resistance is 2000 Ω.