LED Resistor Calculator

Calculate the correct resistor value for your LED circuit based on supply voltage and LED specifications.

V
mA
Resistor Value: -
Power Rating: -
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Understanding LED Resistor Calculations

Properly calculating the resistor value for your LED circuit is crucial to prevent damage and ensure optimal performance. Here's what you need to know:

LED Voltage Drop by Color

LED Color Forward Voltage (Vf) Typical Current
Red2.0V20mA
Green2.1V20mA
Blue3.6V20mA
White3.6V20mA
Yellow2.1V20mA
Orange2.2V20mA
Amber2.1V20mA
Infrared1.7V20mA

How to Use This Calculator

  1. Enter your power supply voltage (usually 5V, 9V, or 12V)
  2. Select your LED color (this sets the forward voltage automatically)
  3. Adjust the forward current if needed (typically 20mA)
  4. Enter the number of LEDs if you're connecting multiple in series
  5. Click calculate to get the recommended resistor value and power rating