Ohms Law Calculator

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Ohms law calculator is used to find resistance, voltage, and current in a circuit. If two values are known from these three values, another one can be found using our vape coil calculator. For example, if the voltage and current are known, you can find the resistance, or if resistance and voltage are known, current can be calculated by entering the other two values in the resistance calculator.

We will discuss Ohm's Law, its formula, calculations, applications of Ohm law, and much more in this post.

What is Ohm's Law?

Ohm's Law is one of the most basic and important electric and electronic circuit laws. It refers to a linear device's current, voltage and resistance so that the third can be calculated if two are known. It means that the Ohm Law is also extremely important because current, voltage, and resistance are three of the main circuit quantities.

Ohm's Law states that the current flowing into a circuit is directly proportional to the potential difference and inversely proportional to the circuit resistance.

In other words, the current often increases by increasing the voltage over a wire. However, the current will fall by half if the resistance is doubled. The unit of resistance is expressed in Ohms in this mathematical relationship.

Ohm's Law symbol

Symbol of Ohm is denoted by Ω letter. It is the System International derived unit of electrical resistance, named after German physicist Georg Simon Ohm.

Ohm's Law Equation

Ohms law formula can be mathematically expressed:

\(V = IR\)

In this equation: 
V = voltage expressed in Volts
I = current expressed in Amps
R = resistance expressed in Ohms

Ohm's Law Wheel

The formula wheel below represents the relationship between P, R, V, and I in Ohm's Law. This is primarily done by the above calculator and is a representation of the algebraic manipulation of the above equation. Pick the equation to be solved in the centre of the wheel and use the relationship for the two common variables in the circular cross-section.

Ohm's law triangle

In order to keep in mind the formula, a triangular shape can be used to represent voltage, current, and resistance. This is sometimes referred to as the Ohm's Law triangle.

The symbol V is in the top corner of Ohm's triangle, the letter I is in the left corner, and the lower right corner is R, as shown in the diagram below.

Ohm's law Triangle

Cover the unknown quantity and evaluate the equation using the remaining quantities. When two quantities are in the same line it means they are multiplying with each other and if two quantities are in the opposite direction (top and bottom), it means they are in the form of division. For example, the voltage is divided by the current if resistance has to be calculated i.e. \(R = \dfrac{V}{I}\).

Ohm's law triangle Formulas for V, I and R

All of these quantities can be calculated in the same way. Use the above diagram to remember the formulas for all three of them.

Check some of our other calculators:

How to calculate power, resistance, and voltage?

The Ohm's Law serves as an algebraic formula for measuring the current in the presence of resistance and the potential difference. If two parameters in the equation are known, it is also easy to calculate the unknown third parameter as calculated below.

1.    Let's find Voltage V

We can calculate the voltage if current and resistance are known by using this equation.

\(V = IR\)


Suppose there is 2 ampere of current and 200-ohm resistance in a wire. Calculate the voltage by using these two quantities?

Step1: First of all, identify the values.

\(V = ?, I = 2 A, R = 200 \Omega\)

Step2: Write down the Ohm's equation.

\(V = IR\)

Step3: Substitute values in the equation and solve.

\(V = 2 \times 200 = 400\)

\(V = 400 volts\)

2.    Let's find Power (P)

We can calculate power if current and voltage are known by using this watt formula.

\(P = I V\)


Suppose there is 4 amperes of current and 20 volts voltage in a circuit. Calculate the power by using these two quantities?

Step1: First of all, identify the values as we did above.

\(P =?, I = 4 A, V = 20 volts\)

Step2: Write down the wattage formula to calculate power.

\(P = IV\)

Step3: Substitute values in the watt equation.

\(P = 4 \times 20 = 40\)

\(P = 40 watts\)

3.    Find Resistance R

We can calculate resistance if the voltage and current are known by using this equation.

\(R = \dfrac{V}{I}\)


Suppose there are 3.5 amperes current and 32 volts in a circuit. Calculate the resistance by using the given quantities?

Step1: We will identify values first.

\(R =?, I = 3.5 A, V = 32 volts\)

Step2: Write down the Ohm's equation for resistance.

\(R = \dfrac{V}{I}\)

Step3: Substitute values in the equation above.

\(R = \dfrac{32}{3.5} = 9.14\)

\(R = 9.14 \Omega\)

How to use ohms law calculator?

Ohms Calculator can be used to calculate voltage, current, and resistance in a circuit for the given values. Ohm calculator makes these calculations very easy, as you can see above, the manual calculations of these quantities are somewhat complex. If you are familiar with the concepts, it could be easy, but if not, calculating manually could be a headache.

To use the ohm law calculator, identify the term you want to calculate.

For voltage, enter resistance and current in the given input boxes. It will give you the voltage instantly for the given values.

For current, enter voltage and resistance in the corresponding input boxes. You will get current in the circuit for the given values.

For resistance, enter current and voltage in the given input boxes. For provided values, milliamp calculator will give you the resistance in ohms instantly.

You don't need to hit any button because the voltage calculator will calculate your value in real-time. You can see the result in the very next text box where you entered your values. It is also known as a vape ohm calculator.

Ohm's Law for AC circuits

There are a number of ac circuits that only have resistance. These circuits are governed by the same rules as dc circuits. Examples of resistive elements include resistors, lamps, and heating elements. If an AC includes only resistance, the AC circuit is also subject to Kirchhoff's Law, Ohm's Law, and the different rules related to DC voltage, current, and power. The Ohm's law equation can be written in an AC circuit as follow:

\(I_{eff} = \dfrac{E_{eff}}{R}\)

Note, all AC current and voltage values are described as effective values unless otherwise specified. The Ohm's Law formula in an AC circuit for average, max, and peak to peak current can be expressed as:

\(I_{avg} = \dfrac{E_{avg}}{R}\)

\(I_{max} = \dfrac{E_{max}}{R}\)

\(I_{peek-to-peek} = \dfrac{E_{peek-to-peek}}{R}\)

Do not mix values of AC, and it is important to remember. All values in the formula must be effective values if you are looking for effective values. Therefore, all values you use must be average values when solving the average values. After you have the following problem, this should be clearer.


 If there are two resistors, R= 6 ohms and R= 10 ohms, on a series circuit and 100 volts alternating voltage source. What will be the avg?

Given Values:

\(R_{1}= 6 \Omega\)

\(R_{2}= 10 \Omega\)

\(R_{s}= 100 V\)

Step1: First, we will calculate the total resistance.

\(R_T = R_1 + R_2\)

\(R_T = 6 + 10 = 16 \Omega\)

Step2: An effective value (as this is not stated otherwise) is inferred for the alternating voltage. Here we will use the Ohm's Law formula for AC circuits.

\(I_{eff} = \dfrac{E_{eff}}{R}\)

Step3: Place the values in the above equation:

\(I_{eff}= \dfrac{100 v}{16 \Omega}\)

\(I_{eff}= 16.67 A\)

Step4: Nonetheless, the question demanded the average current value avg. In order to convert the effective current value to the average current value, the peak-to-peak or maximum current value must be calculated first.

\(I_{max}= 1.414 \times I_{eff}\)

\(I_{nax} = 1.414 \times 16.67 A\)

\(I_{max} = 23.57 A\)

Step5: Now, place the value of I max in avg  equation to get average current in the circuit.

\(I_{avg} = 0.636 \times I_{max}\)

\(I_{avg} = 0.636 \times 23.57 A\)

\(I_{avg} = 14.99 = 15 A\)             

Note that you can use Ohm's Law equations to solve a strictly resistive alternating current circuit problem. Use these equations to solve a direct current circuit problem in the same way.

Table for Metal Resistivity

Below is the Ohm's law chart for resistivity and conductivity. This ohm law chart can be used to get the resistivity and conductivity of metals.


ρ (Ω•m) at 20 °C

σ (S/m) at 20 °C


\(1.59 \times 10^{-8}\)

\(6.30 \times 10^{7}\)


\(1.68 \times 10^{-8}\)

\(5.96 \times 10^{7}\)

Annealed copper

\(1.72 \times 10^{-8}\)

\(5.80 \times 10^{7}\)


\(2.44 \times 10^{-8}\)

\(4.10 \times 10^{7}\)


\(2.82 \times 10^{-8}\)

\(3.5 \times 10^{7}\)


\(3.36 \times 10^{-8}\)

\(2.98 \times 10^{7}\)


\(5.60 \times 10^{-8}\)

\(1.79 \times 10^{7}\)


\(5.90 \times 10^{-8}\)

\(1.69 \times 10^{7}\)


\(6.99 \times 10^{-8}\)

\(1.43 \times 10^{7}\)


\(9.28 \times 10^{-8}\)

\(1.08 \times 10^{7}\)


\(1.0 \times 10^{-7}\)

\(1.00 \times 10^{7}\)


\(1.06 \times 10^{-7}\)

\(9.43 \times 10^{6}\)


\(1.09 \times 10^{-7}\)

\(9.17 \times 10^{6}\)

Carbon steel

\( 10^{10}\)

\(1.43 \times 10^{-7}\)


\(2.2 \times 10^{-7}\)

\(4.55 \times 10^{6}\)


\(4.20 \times 10^{-7}\)

\(2.38 \times 10^{6}\)

Grain-oriented electrical steel

\(4.60 \times 10^{-7}\)

\(2.17 \times 10^{6}\)


\(4.82 \times 10^{-7}\)

\(2.07 \times 10^{6}\)


\(4.9 \times 10^{-7}\)

\(2.04 \times 10^{6}\)

Stainless steel

\(6.9 \times 10^{-7}\)

\(1.45 \times 10^{6}\)


\(9.8 \times 10^{-7}\)

\(1.02 \times 10^{6}\)


\(1.10 \times 10^{-6}\)

\(9.09 \times 10^{5}\)


\(5 \times 10^{-7}\hspace{5px}\text{to}\hspace{5px}10 \times 10^{-3}\)

\(5 \times 10^{-8}\hspace{5px}\text{to}\hspace{5px}10^{3}\)

Carbon (amorphous)

\(5 \times 10^{-4}\hspace{5px}\text{to}\hspace{5px}8 \times 10^{-4}\)

\(1.25\hspace{5px}\text{to}\hspace{5px}2 \times 10^{3}\)

Carbon (graphite)

\(2.5 \times 10^{-6}\hspace{5px}\text{to}\hspace{5px}5.0 \times 10^{-6}\) //basal plane
\(3.0 \times 10^{-3}\) ⊥basal plane

\(2\hspace{5px}\text{to}\hspace{5px}3 \times 10^{5}\) //basal plane
\(3.3 \times 10^{2}\) ⊥basal plane

Carbon (diamond)

\(1 \times 10^{12}\)

\(\sim 10^{-13}\)


\(4.6 \times 10^{-1}\)



\(2 \times 10^{-1}\)


Drinking water

\(2 \times 10^{1}\hspace{5px}\text{to}\hspace{5px}2 \times 10^{3}\)

\(5 \times 10^{-4}\hspace{5px}\text{to}\hspace{5px}5 \times 10^{-2}\)


\(6.40 \times 10^{2}\)

\(1.56 \times 10^{-3}\)

Wood (damp)

\(1 \times 10^{3}\hspace{5px}\text{to}\hspace{5px}4\)


Deionized water

\(1.8 \times 10^{5}\)

\(5.5 \times 10^{-6}\)


\(10 \times 10^{10}\hspace{5px}\text{to}\hspace{5px}10 \times 10^{14}\)


Hard rubber

\(1 \times 10^{13}\)


Wood (oven dry)

\(1 \times 10^{14}\hspace{5px}\text{to}\hspace{5px}16\)



\(1 \times 10^{15}\)



\(1.3 \times 10^{16}\hspace{5px}\text{to}\hspace{5px}3.3 \times 10^{16}\)

\(3 \times 10^{-15}\hspace{5px}\text{to}\hspace{5px}8 \times 10^{-15}\)

Paraffin wax

\(1 \times 10^{17}\)


Fused quartz

\(7.5 \times 10^{17}\)

\(1.3 \times 10^{-18}\)


\(10 \times 10^{20}\)



\(10 \times 10^{22}\hspace{5px}\text{to}\hspace{5px}10 \times 10^{24}\)



Ohm's Law History

A central theorem used for the analysis of electric circuits is Ohm's Law. It states that the potential difference between two points on a circuit is proportional to the product of the current between these two points and the overall resistance between these two points of all electrical instruments. The higher the battery voltage or potential difference, the higher the output in the current. Likewise, less current should arise with greater resistance.

Ohm’s full name was Georg Simon Ohm and was born in 1787 and entered the University in Erlangen in 1805, where he was awarded a PhD. He taught algebra at schools in his city and performed experimental studies in a physics lab of the school. He was actually trying to master electromagnetism theory. In 1817 he was designated to the Jesuits College in Cologne as professor of mathematics.

In 1826 he published articles on the way heat in Fourier's studies was carried out in a quantitative manner. Ohm published Mathematisch bearbeitet, Die galvanische Kette in May 1827, which described the relationship between force, current, and resistance later referred to as the Ohm's Law. On 8 January 1826, Ohm attained the data from his experiments from which he first made his Law. Nevertheless, following his initial release, his studies received a mixed welcome, and he resigned at Cologne and finally took a new professorship at Nürenberg in 1833.

The work of Ohm will catalyze new electricity work in the decades to come. In 1841, Ohm received the Copley Medal, which is the Royal Society's highest award. In 1872, the term "Ohm" was used as the electrical resistance unit.

Uses of Ohm's Law in real World

Throughout our daily life, there are thousands of uses of Ohm's Law. In this post, we will only demonstrate a few of them.

  • The traditional domestic fan controller or regulator is a very common application of Ohm's Law, regulating the fan resistor of the regulator circuit.
  • This rule is used in separating voltage into the output resistance in the voltage divider circuit.
  • There are multiple uses in electronic circuits where deliberate voltage drop is required to deliver particular voltage across various electronic components. Ohm's Law is used to perform this specifically.
  • A shunt is used to avert current in primarily DC ammeter and other DC measuring instruments. Ohm's Law is also used for this purpose.