Enter any two of voltage, current, resistance or power — get the other two instantly.
Ohm's law ties together the four basics of any DC circuit: voltage (V), current (I), resistance (R) and power (P). The core equations are V = I × R and P = V × I. Give this calculator any two of the four and it returns the other two, using rearrangements like R = V/I, I = P/V and P = I²R. It's ideal for LED resistors, wiring, power supplies and electronics projects.
Volts = amps × ohms. Watts = volts × amps. To find a resistor for an LED, divide the voltage you need to drop by the LED current. To check a supply won't overload, work out the power the load draws. Everything here is DC / resistive — AC circuits with reactance need extra terms.
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