Ohms Law Calculator + Online Solver With Free Steps

The online Ohms Law Calculator is a free tool that helps you find the values of parameters involved in ohm’s law.

There are three parameters involved in ohm’s law, which are voltage, resistance, and current. So the calculator takes values of any two parameters and using ohm’s law formula returns the value for the third parameter.

ohms law calculator

What Is the Ohms Law Calculator?

The Ohms Law Calculator is an online tool that is specifically designed to quickly solve problems related to ohm’s law.

Ohm’s law is one of the elemental laws in the electrical and magnetism domain. It explains how the current varies if the voltage changes. Many real-life problems include finding the value of voltage or current.

Such types of problems then use ohm’s law to determine these electrical parameters. It is a simple formula, you just need to make some mathematical manipulations according to your target parameter.

You can use the Ohms Law Calculator instead of solving these problems manually. It solves any kind of complex problem or finds anyone among the three parameters in a matter of seconds.

To access this tool you need a good internet connection and browser. There is no need to download or install any application at all. It is one of the online tools available.

It is a strong tool that helps students, and electrical engineers, fix their problems. To get further information about the calculator like how to use it and the working algorithm at the backend of the calculator, refer to the coming section.

How To Use the Ohms Law Calculator?

You can use the Ohms Law Calculator by putting any two variables into the provided spaces. The calculator is very easy to comprehend because of its simplicity.

The calculator has three input boxes; the first one is to select the target quantity and the rest two boxes for entering the values for the variables. After putting these values, you just need to press a button to get the final solution to your problem. Once you know which quantity you want to find and which quantities are available, you are ready to use this calculator.

To get the perfect solutions from the calculator, there is a detailed guideline that you must follow. The detailed steps to use the calculator are given below:

Step 1

Select one among the three available options for the electrical parameters in the ‘Calculate‘ field. This is the parameter whose value you want as a result.

Step 2

Insert the first parameter of your problem in the first box labeled with the word ‘If. Make sure to enter the appropriate unit with the numerical value for the parameter.

Step 3

Now enter the value of the second parameter in the next box mentioned as And along with its unit.

Step 4

To acquire the final solution, press the ‘Submit‘ button in black color.


The output of the calculator depends on the desired parameter. It can find all parameters but one at a time. If the desired parameter is voltage or current, then it will display the resultant parameter in three different units

If the resistance is required as a result, then it will give the value with three different units. Also, it will give the picture of resistance with the respective colors on it. It helps the user to visualize the resistor and verify the value using the color code method.

How Does the Ohms Law Calculator Work?

The Ohms’s law calculator works by finding the value of resistance, current, and voltage by applying Ohm’s law. It calculates one unknown quantity when two known quantities are given.

This calculator will be good to use when there is knowledge about ohm’s law and the relationship between the voltage and current.

Ohm’s Law

Ohm’s Law defines the relationship between the current and voltage. It states that “ the current flowing between two points of an electrical conductor is directly proportional to the voltage or potential difference across that two points.”

Ohm’s law can be written mathematically as:

V $ \propto$ I

V = I*R

Where ‘R‘ is the proportionality constant and is called the Resistance of the conductor, ‘V‘ is the voltage across two points, and ‘I‘ is the flowing current between two ends of the conductor.

This law introduces a new quantity which is resistance. Its SI unit is ohms and denoted by a symbol $\Omega$. 

Ohm’s law is the most commonly used in electrical physics because along with the current, voltage, and resistance it also calculates the power and efficiency of the circuit.

However, it is only applicable where the physical condition such as the temperature of the circuit does not change.

Components of Ohm’s Law

The working rule of Ohm’s law consists of its three major components which are voltage, current, and resistance but before explaining these concepts, we should know about the electric field.

Electric Field

An electric field is a physical medium that surrounds an electrically charged particle and that particle experiences an electric force. It is formed when the current flows due to the potential difference across two points.

It is a vector quantity and envisioned as lines directing toward a negative charge that is radially inwards or directing away from a positive charge means radially outwards.


When the current is flowing from one end to the other in an electric field it creates a difference in the quantity of charge between the two ends. This potential difference is called voltage. The SI unit of voltage is the volt represented by V.


The rate of flow of electric charge or electrons in an electric field is known as current. The electrons start to move from one location to another due to their loose bonding among them. This movement of electrons is termed electric current.

Its SI unit is ampere and measured in coulombs per second.


The literal meaning of resistance is opposition or to stop something. In electrical physics, resistance is the measure of the opposition to the flow of an electric current. It resists the movement of electrons from one spot to another.

The resistance of a circuit or a wire of uniform cross-section depends on a few factors that affect it. It depends directly on the length of the wire as the length increases the resistance also increases.

It is also inversely related to the area of the wire. Thick wire has less resistance and vice-versa. The temperature of the wire or any conductor also affects its resistance. The resistance increase with the temperature rise.

Whereas there is less resistance when the temperature gets lower. The relation of the above factors with the resistance at a specific temperature can be expressed mathematically as:

R = $\rho$ (L/A)

Where ‘L‘ is the length of the wire, ‘A‘ is the cross-sectional area and $\rho$ is the specific resistance or resistivity of the material of the wire or conductor.

The resistivity of the material is its attribute which offers resistance in the circuit. The resistivity is low when the current is passing through the material which is a good conductor and when the current is flowing through an insulator material, there is more resistivity.

Current-Voltage Relationship

Current and voltage are closely linked to each other. Ohm’s law defines the relationship between voltage and current. It states that the ratio of voltage to current remains constant for the given resistance. 

Hence there is a linear graph between the voltage and current.

Determining the Power of a Circuit

The power can be calculated by using Ohm’s law formula. The power is the product of voltage and current that is given by:

P = V*I         (1)

By ohm’s law, it is known that V=I*R. When putting this into the above equation it results in the following new formula:

P = (I*R) I = $I^2$*R

The above formula is known as the resistive heating formula or ohmic loss formula.

Again by ohm’s law, we know that ‘I=V/R’ and by letting it into the equation (1), it leads to another formula that is shown below:

P = V (V/R) = $V^2$/R

This relation is used to find power dissipation in the resistance. The above two formulae are also used to calculate the resistance of the circuit if the power is known.

Solved Examples

To further clarify the working phenomena of the calculator, let’s solve some interesting problems one by one.

Example 1

Consider a voltage source that supplies 12 V to an electric bulb and the current passing through it is 8 mA. Calculate the resistance of this bulb.


The solution to this problem can be easily determined using the calculator. It gives the following results.

Parameter Value

The resistance of the bulb is given below in three different units.

Electrical Resistance = 1.5 $k\Omega$ (kiloohms) = 0.0015 $M\Omega$ (megaohms) = 1500 $\Omega$ (ohms)

Resistance Color Code

Figure 1 shows the color code for the resultant resistance of the bulb.

ohms law resistance color code example 1

Figure 1

Example 2

An electric iron has a potential difference of 550 volts and a resistance of 170 $\Omega$. Find the current flowing through the iron.


According to the given data the problem’s solution is given below.

Parameter Value

The current can easily be determined using the Ohms law calculator by inserting the values of given voltage and resistance.

Electric current = 3.235 A (amperes) = 0.003235 kA (kiloamperes)

All the Mathematical Images/Graphs are created using GeoGebra.

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