Ohm's Law
Calculate resistance and power from voltage and current using Ohm's Law.
Results
What is it?
Ohm's Law is the fundamental relationship in electrical circuits: V = I x R, where V is voltage (volts), I is current (amperes), and R is resistance (ohms). Power (watts) is calculated as P = V x I.
How to use
Enter the voltage across a component and the current flowing through it. The calculator determines the resistance and the power dissipated. This is essential for selecting correct resistors, fuses, and wire gauges.
Example scenario
A 12V car battery powering a 2A headlight bulb: the bulb has 6 ohm resistance and dissipates 24W of power. To determine wire gauge, you need to know the current draw.
Pro tip
When designing circuits, always calculate power dissipation to prevent overheating. A resistor rated for 0.25W carrying 0.5W of power will overheat. Always use components rated for at least 2x the expected power.