Ohm's Law Calculator
A complete tool to calculate Voltage (V), Current (I), Resistance (R), and Power (P). Enter any two known values and solve for the others.
Ohm's Law & Power Wheel
This tool uses Ohm's Law and Watt's Law to calculate circuit properties.
The Foundation of Electronics: Ohm's Law and Power Law
Ohm's Law is the most fundamental principle in all of electronics. It describes the relationship between **Voltage**, **Current**, and **Resistance** in an electrical circuit. Paired with the Power Law (also known as Watt's Law), which relates **Power** to the other three variables, you have a complete toolkit for analyzing and designing basic circuits. This calculator is a flexible tool that lets you solve for any of these four variables by inputting any two you already know.
The Four Key Components Explained
- Voltage (V): Think of it as the "pressure" that pushes electricity through a circuit. It is measured in Volts (V).
- Current (I): This is the rate at which charge is flowing through the circuit. It is measured in Amperes, or "Amps" (A).
- Resistance (R): This is the circuit's opposition to the flow of current. It is measured in Ohms (Ω). You can decode the resistance of a component with our Resistor Color Code Calculator.
- Power (P): This is the rate at which electrical energy is transferred or consumed by the circuit, often dissipated as heat. It is measured in Watts (W).
How to Use the Calculator
- Select what to solve for: Choose Voltage, Current, Resistance, or Power from the tabs at the top. The selected field will become disabled, as it will hold the result.
- Enter two known values: Fill in the numbers and select the appropriate units for any two of the other fields.
- See the instant result: The calculator updates automatically, showing you the calculated value for your selected variable, as well as the other unknown value. For instance, if you enter Voltage and Current to solve for Resistance, the Power will also be calculated and displayed.
Practical Applications for Ohm's Law
- LED Circuits: Calculating the correct current-limiting resistor to use with an LED to prevent it from burning out.
- System Sizing: Determining the power consumption of a device to select the right power supply.
- Circuit Analysis & Troubleshooting: Verifying that a circuit is behaving as expected by measuring two values and calculating the third.
- Wire Safety: Understanding how resistance affects current can help in choosing the right wire gauge to prevent overheating. Our Voltage Drop Calculator is a specialized tool for this purpose.