Ohm's Law Calculator

Ohm's law links voltage, current and resistance in an electrical circuit.

How the Math Works

Ohm's Law reveals the fundamental relationship between voltage (V), current (I), and resistance (R) in electrical circuits. The formula I = V ÷ R shows that current is directly proportional to voltage and inversely proportional to resistance. When voltage increases, current increases proportionally, but when resistance increases, current decreases. For power calculations, P = V² ÷ R demonstrates how power is related to the square of voltage and inversely to resistance, meaning small voltage increases can dramatically boost power consumption.

Practical Applications

To use this calculator, simply input the known voltage and resistance values. The calculator automatically determines the current by dividing voltage by resistance (I = V/R). It then calculates power by squaring the voltage and dividing by resistance (P = V²/R). For example, a 12V battery connected to a 4Ω resistor yields 3A of current and 36W of power. This eliminates manual calculations and reduces errors in circuit design and troubleshooting.

Day-to-Day Use

Understanding these calculations helps you choose the right electrical components for everyday projects. When replacing a fuse, you can calculate if it will handle the required current. Selecting appropriate wire gauge becomes easier when you know the current your device will draw. For household electronics, this knowledge prevents overheating and potential fire hazards by ensuring appliances don't exceed safe power ratings. Even when buying batteries or choosing LED lights, these calculations help you make informed decisions about energy efficiency and safety.

Worked example

12 V across 4 Ω → I = 3 A, P = 36 W.

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