LED Series Resistor Calculator

Selecting the correct series resistor is critical for LED circuits. This tool automates the process by allowing you to select your LED Color and the Number of LEDs in your chain.

Crucially, it calculates the Power Dissipation and suggests a safe Resistor Wattage (e.g., 1/4W, 1/2W) to prevent overheating.

Circuit Details

Input

Source Voltage (Vs)

LED Color

Forward Voltage (Vf)

LED Current (If)

LEDs in Series

Pcs

Component Selection

Output

Resistance (R)

Nearest Standard

E24

Rec. Wattage

Size

Actual Heat

Design Notes

Ensure your Source Voltage is higher than the total LED voltage ($V_f \times Count$).
Wattage recommendation uses a 2x safety factor.

Reference: Typical Forward Voltages (Vf)

Different LED colors require different voltages to operate. You can check your specific datasheet or use this standard reference table.

LED Color	Typical Vf Range
Red	1.8V – 2.1V
Amber	2.0V – 2.2V
Orange	1.9V – 2.2V
Yellow	1.9V – 2.2V
Green	2.0V – 3.1V
Blue	3.0V – 3.7V
White	3.0V – 3.4V

How to Use This Calculator

Determine component values for safe LED operation.

Enter Circuit Details

Input your Source Voltage and select the LED Color. If you are connecting multiple LEDs in a chain, increase the LEDs in Series count.

Set Target Current

Input the desired LED Current (If). Standard LEDs typically use 20mA. High-brightness LEDs may use more.

Select Component

Use the Nearest Standard Resistor and the recommended Wattage (e.g., 1/4 Watt) to choose the right part for your circuit.