Ohm's Law Calculator
Input any two known principles (Voltage, Current, Resistance, or Power) and we will automatically solve for the missing variables.
Ohm's Law & Power Equation
Awaiting Inputs
Ohm's Law Calculator: Voltage, Current, and Resistance
Ohm's Law is the absolute foundational principle of all electrical engineering and circuit design. Formulated by German physicist Georg Ohm in 1827, it defines the mathematical relationship between Voltage, Current, and Resistance in any electrical circuit. The Calculay Ohm's Law Calculator allows you to instantly solve for any missing variable, ensuring your circuits are safe, efficient, and properly balanced.
The Three Pillars of Electricity
To understand Ohm's Law, it is highly useful to visualize electricity flowing through a wire exactly like water flowing through a garden hose:
- Voltage (V) - Measured in Volts: This is the water pressure. It is the electrical force pushing the electrons through the wire. A 9V battery pushes harder than a 1.5V AA battery.
- Current (I) - Measured in Amperes (Amps): This is the volume of water actually flowing out of the hose. It represents the quantity of electrons moving past a specific point per second. High current is what makes electricity dangerous to humans.
- Resistance (R) - Measured in Ohms (Ω): This is a kink in the hose. It represents any material or component (like a lightbulb or a physical resistor) that restricts the flow of electrons, causing friction and often generating heat or light.
The Core Equations
The relationship between these three elements is locked into a strict mathematical triangle. If you know any two values, you can always calculate the third:
- To find Voltage: V = I × R (Current multiplied by Resistance)
- To find Current: I = V / R (Voltage divided by Resistance)
- To find Resistance: R = V / I (Voltage divided by Current)
Practical Application: LED Protection
Imagine you are building a hobby project. You have a 12V power supply, and you want to light up a small red LED. If you connect the LED directly to the 12V supply, the current (I) will be massive because the LED has almost zero resistance. The LED will violently pop and burn out instantly.
By checking the LED's datasheet, you see it requires exactly 20mA (0.02 Amps) to light up safely. Using Ohm's Law (R = V / I), you calculate R = 12 / 0.02. You now know you must wire a 600-Ohm resistor into the circuit to restrict the current and protect the LED.