2000+
Tools
50K+
Active Users
1M+
Files Processed
99.9%
Uptime
Use this free Ohm's Law Calculator to instantly solve any unknown variable in the fundamental Ohm's Law equation — V = I × R — the cornerstone of all electrical circuit analysis. Enter any two known electrical values to automatically solve the third: Voltage (V = I × R) in Volts (V) · Current (I = V / R) in Amperes (A) or milliamps (mA) · Resistance (R = V / I) in Ohms (Ω), kΩ, or MΩ — with automatic unit conversion across all standard electrical units and instant cross-calculation of Power (P = V × I = I²R = V²/R) in Watts (W) — giving you a complete Ohm's Law and power triangle solution in a single calculation.
This online V = IR calculator is trusted across every level of electrical and electronics engineering: A-Level, GCSE, AP Physics, JEE, and NEET Ohm's Law exam problems, DC circuit analysis — series and parallel resistor networks, LED current limiting resistor calculation, battery and power supply voltage regulation, PCB trace current capacity and voltage drop analysis, Arduino, Raspberry Pi, and electronics prototyping calculations, solar panel and battery system sizing, and electrical fault diagnosis and troubleshooting. Ohm's Law — first formulated by Georg Simon Ohm in 1827 — states that the current through a conductor is directly proportional to voltage and inversely proportional to resistance, forming the mathematical foundation of all DC circuit theory, electronics design, and electrical engineering. Trusted by students, electricians, electronics hobbyists, PCB designers, and electrical engineers worldwide.
Ohm’s Law is one of the most fundamental principles inelectrical engineering and physics. It describes the relationship betweenvoltage, current, and resistance in an electrical circuit. This law explains how electric current flows through a conductor and how it is affected by voltage and resistance.
The concept was discovered by the German physicist Georg Simon Ohm in 1827. Through experiments, he observed that the electric current passing through a conductor is directly proportional to the voltage applied and inversely proportional to the resistance of the conductor.
Because of its simplicity and accuracy, Ohm’s Law is widely used in electronics, electrical circuits, power systems, and engineering design. Engineers and students use an Ohm’s Law calculator to quickly determine unknown electrical values when two of the three variables are known.
Understanding Ohm’s Law is essential for designing circuits, troubleshooting electronic devices, calculating electrical power, and ensuring safe electrical system operation.
Whether you are a student studying physics, an electrician working on circuits, or an engineer designing electronic systems, the Ohm’s Law formulais one of the most important tools used to analyze electrical behavior.
The basic Ohm’s Law formula expresses the relationship between voltage, current, and resistance in an electrical circuit.
This formula means that the voltage across a conductor is equal to the current flowing through it multiplied by the resistance of the conductor.
The formula can also be rearranged to calculate current or resistance when the other values are known:
These three equations make Ohm’s Law extremely flexible and useful in electrical analysis. By measuring or knowing any two variables, you can easily calculate the third value using an Ohm’s Law calculator.
The relationship between voltage, current, and resistance forms the foundation of most electrical circuit calculations and helps engineers understand how electricity behaves in real-world systems.
Understanding Ohm’s Law becomes easier when applied to practical circuit examples. Suppose a resistor in a circuit has a resistance of 10 Ω and the current flowing through it is 2 A.
Using the Ohm’s Law formula:
This means the voltage across the resistor is 20 volts.
Let’s look at another example. If a circuit has a voltage of12 V and resistance of 6 Ω, the current flowing through the circuit would be:
These simple calculations show how engineers determine electrical properties in circuits. An Ohm’s Law calculator simplifies these calculations and instantly provides accurate results.
In real electrical systems, Ohm’s Law is used to analyze circuits in household wiring, electronic devices, power supplies, and industrial electrical equipment.
Ohm’s Law is also closely related to electrical power calculations. Electrical power represents the rate at which electrical energy is converted into other forms of energy such as heat, light, or mechanical work.
The basic electrical power formula is:
Where:
By combining the power formula with Ohm’s Law equations, additional formulas can be derived:
These formulas allow engineers to calculate electrical power in circuits when different variables are known. Power calculations are important for designing safe circuits and ensuring that components such as resistors and wires can handle the electrical load.
For example, if a device draws excessive power, it may overheat and cause damage or electrical hazards. That is why electrical engineers rely onOhm’s Law and power formulas when designing electronic systems.
The following table provides a quick reference for calculating voltage, current, and resistance using Ohm’s Law formulas. This reference chart is commonly used by students, electricians, and engineers when analyzing electrical circuits.
| To Calculate | Formula | Required Values |
|---|---|---|
| Voltage (V) | V = I × R | Current and Resistance |
| Current (I) | I = V ÷ R | Voltage and Resistance |
| Resistance (R) | R = V ÷ I | Voltage and Current |
Electrical engineers often visualize Ohm’s Law using the famousOhm’s Law triangle, which helps quickly remember how the formulas relate to each other.
Understanding this relationship is essential for solvingelectrical circuit problems, designing electronic devices, and learning the fundamentals of physics and electrical engineering.
Modern tools such as an Ohm’s Law calculator make these calculations fast and accurate, helping students and professionals quickly determine voltage, current, resistance, and power in electrical systems.
Ohm’s Law states that voltage equals current multiplied by resistance. It describes the relationship between electrical voltage, current, and resistance in a circuit.
Yes. Enter voltage and resistance to calculate current using the formula I = V ÷ R.
This calculator is designed primarily for basic DC circuit calculations. AC circuits often require impedance instead of simple resistance.
Resistance can be calculated using R = V ÷ I, where V represents voltage and I represents current.
Voltage is measured in volts (V), current in amperes (A), and resistance in ohms (Ω).
Yes, but resistance is replaced by impedance when analyzing alternating current circuits.
Yes. However, total resistance must first be calculated depending on whether the circuit is series or parallel.
Yes. This online calculator is completely free and provides instant electrical calculations.
Voltage represents the electrical potential difference that drives current through a circuit.
Current is the flow of electric charge through a conductor and is measured in amperes.
Resistance is the opposition to the flow of electric current through a material.
Ohm’s Law helps engineers calculate voltage, current, and resistance when designing and analyzing electrical circuits.
The Ohm’s Law triangle is a visual method used to remember the relationships between voltage, current, and resistance.
Electrical power can be calculated using P = V × I or using Ohm’s Law variations such as P = I²R or P = V² ÷ R.
Electrical power is the rate at which electrical energy is transferred or consumed in a circuit.
Materials like rubber, glass, and ceramics have high resistance and are commonly used as electrical insulators.
Metals such as copper, aluminum, and silver have very low resistance and are commonly used as electrical conductors.
A DC circuit uses direct current where electricity flows in one constant direction.
An AC circuit uses alternating current where the direction of current periodically changes.
If resistance increases while voltage remains constant, the current decreases according to Ohm’s Law.
If voltage increases while resistance remains constant, the current increases proportionally.
Impedance is the total opposition to current flow in an AC circuit, combining resistance and reactance.
Ohm’s Law is used in electrical engineering, electronics design, power systems, robotics, and telecommunications.
Yes. This Ohm’s Law calculator helps students understand the relationship between voltage, current, and resistance.
Ohm’s Law is one of the most fundamental formulas used in electrical engineering and electronics circuit design.