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.

## FAQ

**What is a LED resistor?**

The LED resistor is the total resistance needed for a simple LED circuit in order for it to work properly.