Electronics and Circuit Calculators: Ohm's Law, Resistors and Voltage Drop
Circuit problems rely on a handful of relationships: V = IR, P = VI, and the rules for series and parallel resistors. These calculators solve for the unknown quantity and show the equation used, helping students and hobbyists verify their designs and homework.
4 free electronics / circuits calculators
Ohm's Law Calculator
Fill in any two of Voltage, Current and Resistance to solve for the rest.
Open calculator →Voltage Drop Calculator
Voltage drop over a copper wire run, from gauge, length and current.
Open calculator →Resistor Calculator
Decode a 4-band resistor color code into its resistance value.
Open calculator →Electricity Calculator
Estimated running cost of an appliance, from wattage and usage.
Open calculator →Frequently asked questions
What is Ohm's law?
Ohm's law states V = I × R: the voltage across a resistor equals the current through it times its resistance.