How do I read the resistor color code?

This calculator generates a standard 4-band code. The first two bands represent the significant digits, the third band is the multiplier (number of zeros), and the fourth (Gold) represents 5% tolerance.

LED Series Resistor Calculator & Color Code Visualizer

LED Resistor Calculator | Visual Color Code & Wattage Guide

Calculates the precise current limiting resistor value for your LED circuits. This tool uses Ohm’s Law to ensure your Light Emitting Diodes operate safely without burning out.

Circuit Details

Input

Source Voltage (Vs)

LED Color

Forward Voltage (Vf)

LED Current (If)

LEDs in Series

Pcs

Component Selection

Output

Part Preview

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Ideal Resistance

E24 Standard

Min. Wattage

Size

Design Note

Values calculated for safety (2x power factor).

Typical Forward Voltages (Vf)

Color	Voltage (V)	Description
Red	1.8 – 2.1	Standard indicator.
Amber	2.0 – 2.2	Cautionary signal.
Green	2.0 – 3.1	System status OK.
Blue	3.0 – 3.7	Modern digital interface.
White	3.0 – 3.4	High-intensity lighting.

FAQ & Troubleshooting

Why is my LED not turning on?

Check your source voltage. If Vs is lower than the total Vf of your LEDs, the circuit cannot flow current. Ensure Vs is always at least 1V higher than the LED threshold.

How do I determine the wattage size?

This calculator automatically provides a safe wattage recommendation. It uses the formula P = V_drop * If and applies a 2x safety multiplier to ensure the resistor doesn’t overheat during operation.