What Resistor to Use with LED?

LEDs are widely used in electronic devices and lighting systems due to their energy efficiency, long lifespan, and ease of use. However, using LEDs in circuits requires proper consideration of resistors to avoid damage to the LED and ensure optimal performance. In this article, we will discuss the importance of resistors in LED circuits and provide some tips on how to choose the right resistor for your specific LED setup.

Importance of Resistors in LED Circuits

Resistors are crucial components in any electrical circuit as they regulate the flow of current through a circuit. In an LED circuit, a resistor is used to limit the amount of current that flows through the LED. Without a resistor, too much current can pass through the LED causing it to burn out or fail prematurely.

What Resistor to Use with LED?

The value of resistance required for an LED circuit depends on several factors such as the voltage source, forward voltage drop across the LED, and desired brightness level. To calculate the correct resistance value for your particular setup you can use Ohm’s Law which states that V = IR (voltage equals current multiplied by resistance).

To determine what resistor value you need, follow these simple steps:

  1. Determine the voltage source: Check the voltage rating of your power supply or battery.
  2. Find out Forward Voltage Drop: This is usually provided by manufacturers in their datasheets.
  3. Calculate Current: Decide how much current you want flowing through your circuit.
  4. Calculate Resistance: Use Ohm’s law formula R=V/I.

For example, let’s say you have a 9V battery powering an LED with a forward voltage drop of 2V and you want 20mA (0.02A) flowing through your circuit. Using Ohm’s law formula R=V/I, R = (9V – 2V)/0.02A = 350 ohms

Therefore, a 350-ohm resistor would be required for this specific setup.

Additional Tips

It is always better to choose a higher resistance value than needed rather than lower as it prevents excess current from flowing through your circuit which could cause damage or premature failure.

Also keep in mind that different types of LEDs have different forward voltage drops so make sure to check their datasheets before calculating resistance values.


In conclusion, using resistors correctly is crucial when working with LEDs as it prevents damage and ensures optimal performance. By following our guide above you should now have a better understanding of what resistor values are required for your specific LED setup.


  1. LED Resistor Calculator
  2. Ohm’s Law Calculator
  3. Understanding Resistors

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