Electricity/Electronics Calculator
Resistance Calculator
Resistance is the opposition to current flow in an electric circuit, measured in ohms (Ω),...
Read MoreElectric Current Calculator
Electric current is the flow of electrons in one direction and is measured in amperes (A)....
Read MoreVoltage Calculator
Voltage is the electric potential difference that moves charge through a circuit, measured...
Read MoreElectric Power Calculator
Electric power is energy per unit time, the product of voltage and current. Enter voltage ...
Read MoreAbout This Category
Ohm’s law and its power forms cover almost every question about a simple circuit: given any two of voltage, current and resistance, the other two follow. The pages are split by which pair you already know, because that is how the question usually arrives.
All values are SI: volts, amperes, ohms and watts. Household wiring examples use the mains voltage of the country for the selected language, which is 120 V in the United States and 230 V in most of Europe.
Frequently Asked Questions
Which formula should I use?
Enter what you know. Voltage and current give resistance as R = V / I; voltage and resistance give current as I = V / R; current and resistance give power as P = I²R.
Why does a device get hot?
Because power dissipated in a resistance is I²R. Doubling the current quadruples the heat, which is why thin extension leads are rated for less current than the socket supplies.
Does AC change these calculations?
For resistive loads, no. Motors and electronics add reactance, so the real power is lower than volts × amps and the power factor has to be included.
Calculators in This Category
Sources & last update
2026-10-19