Ohm's Law Calculator

Ohm's law is one of the most essential laws of electrical engineering, explaining the relationship between a circuit's resistance, voltage, and current.

Formula

Basic Ohm's law is calculating the relation between voltage, current, and resistance. The following Ohm's law triangle chart will help to visually remember the equation for calculating each parameter. ^[1]

Where:

V - is the voltage with an SI unit of volt, represented by the letter V.
I - is a current value that flows through a circuit with an SI unit of ampere or amp and is represented by the letter A.
R - is the resistance with an SI unit of ohms, represented by the letter Ω.

Calculate voltage

Here is the equation to find the voltage of a circuit with known current and total resistance: Voltage (V) = Resistance (R) × Current (I).

V = R \times I

Calculate resistance

Here is the equation to find the equivalent resistance of a circuit with known voltage and current: Resistance (R) = Voltage (V) / Current (I).

R = \frac{V}{I}

Calculate current

Here is the equation to find the current flows through a circuit with known voltage and equivalent resistance: Current (I) = Voltage (V) / Resistance (R).

I = \frac{V}{R}

Examples

Calculate the current flows through a light bulb.

What current flows through a 5V flashlight bulb with a resistance of 3.6Ω?

Using the following formula, enter the given values to find the current flowing through the flashlight bulb by knowing its voltage and resistance.

$ \text{Current} = \frac{\text{Voltage}}{\text{Resistance}} $

$ {I} = \frac{V}{R} $

$ {I} = \frac{5V}{3.6Ω} $

$ {I} = 1.39A $

So, the current that flows through the 5V flashlight bulb with 3.6Ω resistance is I = 1.39A.

Alternatively, you can use our calculator by going to the CURRENT tab, entering the number 5 into the Voltage (V) box, 3.6Ω into the Resistance (R), and instantly getting the current in A, in this case, 1.39A.

Using our ohms law calculator to calculate current — Using our ohms law calculator to calculate the current

Calculate voltage drops.

Find the voltage drop in an extension cord with a resistance of 0.08Ω with a current flow of 10A.

To find the amount of voltage drop through the extension cord with known current and resistance, use the following formula and enter the given values.

$ \text{Voltage} = \text{Resistance} \times {\text{Current}} $

$ V = R \times I $

$ V = 0.08Ω \times 10A $

$ V = 0.8V $

So, the amount of voltage drops from an extension cord is V = 0.8V.