Ohm's Law Calculator
Calculate voltage, current, resistance, or power using Ohm's Law (V = I × R). Enter any two known values to instantly solve for all four electrical quantities.
About the Ohm's Law Calculator
Ohm's Law (V = I × R) is the foundation of electrical circuit analysis. It states that the voltage across a conductor equals the current through it multiplied by its resistance. From these three quantities, power (P = V × I) can also be derived. Knowing any two values lets you solve for all four. For practical wiring applications, use our Voltage Drop Calculator to ensure wire runs don't lose too much voltage over distance.
Ohm's Law applies to resistive (linear) loads. Non-linear components like diodes, transistors, and motors don't follow a simple V=IR relationship. For component identification, our Resistor Color Code Calculator helps you decode resistor bands to find the resistance value. Once you know the resistance value, enter it here with your supply voltage to find the expected current.
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For a related calculation, use Resistor Calculator to convert resistor color bands to resistance value, or convert a value to its 4-band color code. Alternatively, use Electricity Calculator to calculate electricity cost for multiple appliances. See daily, monthly, and yearly kWh usage and costs.