Electronics · Circuit Math

LED Series Resistor Calculator

Find the current-limiting resistor for your LED, or check the current a resistor you have will give it.

9 V 330 Ω LED ×1
Resistor 330 Ω
Supply voltage
LED forward voltage
LEDs in series
Desired current

Assumes a fixed LED forward-voltage drop — real LEDs vary with current and temperature. Always check your LED's datasheet.