I Googled It For You

Basic electronics

Learn Ohm's Law, then use it.

Enter any two known values to calculate the third, see the circuit power, and follow the math step by step.

Enter any two values

Use the unit menus when your values are written in millivolts, milliamps, or kilohms.

Ohm's Law at a glance

V

Voltage pushes current.

I

Current is the flow.

R

Resistance limits flow.

Ohm's Law triangle with V above I and R, showing V equals I times R, I equals V divided by R, and R equals V divided by I.

Use the triangle as a memory aid: cover voltage to multiply current and resistance, cover current to divide voltage by resistance, or cover resistance to divide voltage by current.

A short lesson

What is Ohm's Law?

Ohm's Law describes the relationship between voltage, current, and resistance in an electrical circuit. Voltage is the electrical pressure, current is the movement of charge, and resistance is the opposition to that movement.

The relationship is named for German physicist Georg Simon Ohm, whose work on electrical circuits was published in 1827. Today, the law is a starting point for understanding batteries, LEDs, resistors, sensors, and many beginner electronics projects.

For example, a 12 V source supplying 2 A through a simple load has 6 ohms of resistance because R = V / I, or 12 / 2. The same circuit uses 24 W of power because P = V x I.

Use it carefully

When is it useful?

Use Ohm's Law to estimate how a known voltage, current, or resistance relates to the others. It can help you check a basic calculation, choose a resistor for a low-voltage project, or understand why a circuit draws more or less current.

This simple calculator is not a complete circuit simulator. Real components have tolerances, temperature limits, changing loads, and power ratings. More complex circuits, alternating current, and household wiring require additional electrical rules and safety knowledge.

Safety note: This tool is for learning and low-voltage DC projects only. Do not use it to plan or work on household mains wiring or live electrical systems. Follow proper safety practices and consult a qualified professional for real-world electrical work.

Disclaimer: This calculator provides educational estimates for basic low-voltage DC relationships. It is not a substitute for electrical training, component datasheets, or professional advice.