LED Resistor Calculator

This calculator is based on Ohm's Law, but takes into consideration the voltage drop from the LED. To use the calculator, enter any three known values and press "Calculate" to solve for the others.


Voltage Source (Es): Volts (V)
Voltage drop from LED (Eled): Volts (V)
Current through the LED (Iled):
Resitance (R):
Power (P): Watts (W)
To calculate the resistor needed for a simple LED circuit, simply take the voltage drop away from the source voltage then apply Ohm's Law.
Resistor formula for LEDs