Enter the voltage source, the voltage drop across the LED, and the current through the LED into the calculator. The calculator will display the needed resistance for the simple circuit.
LED Resistor Formula
The following formula is used to calculate the resistance of an LED circuit.
R = (Vs – Vl)/ IL
- Where R is the resistance
- V is the voltage of the source
- Vl is the voltage drop across the LED
- IL is the current through the LED
LED Resistor Definition
An LED resistor is defined as the total resistance in an LED circuit.
LED Resistor Example
How to calculate LED resistor
- First, determine the source voltage
Measure or calculate the voltage coming from the source.
- Next, measure the voltage drop across the LED
This can be done by measure directly after the LED and subtracting that value from the source voltage.
- Next, measure the current across the LED
Measure or calculate the current across the LED.
- Finally, calculate the resistance
Using the information from steps 1,2 and 3, calculate the LED resistance.
The LED resistor is the total resistance needed for a simple LED circuit in order for it to work properly.