Created By : Vaibhavi Kumari

Reviewed By : Rajashekhar Valipishetty

Last Updated : May 10, 2023

The online LED Resistor Calculator determines the resistor to use in various electronic circuits including LEDs. Fill in the blanks of the calculator with the supply voltage and current via the LED to quickly and conveniently check power consumption in a single LED, all LEDs, and the resistor.

Choose a Calculation
Voltage Source (Vs)
Voltage drop from LED (Vled)
Current through the LED (Iled):

What is meant by LED?

A small electronic gadget is known as an LED (Light Emitting Diode). An LED emits light in various colours such as red, green, and blue when current travels through it. If a large number of current travels through the diode, the LED will be damaged. As a result, we add a resistor to the circuit to limit the current flow via the diode.

The number of LEDs in a circuit might vary. Those LEDs will be connected in a series or parallel format.

LEDs Connected in Series

For LEDs in series, the formulas for calculating resistance and power dissipated are as follows

Resistance R = (V - n * Vₒ) / Iₒ

Power dissipated in a single LED Pₒ = Vₒ * Iₒ

Power dissipated in all LEDs (total) P = n * Vₒ * Iₒ

The power dissipated in the resistor Pr = (Iₒ)² * R

LEDs Connected in Parallel

Here are the formulas for calculating the resistance and power dissipated by LEDs connected in parallel.

Resistance R = (V - Vₒ) / (n * Iₒ)

Power dissipated in a single LED Pₒ = Vₒ * Iₒ

Power dissipated in all LEDs (total) P = n * Vₒ * Iₒ

he power dissipated in the resistor Pr = (n * Iₒ)² * R

  • Where, n = number of LED's connected
  • Vₒ= voltage drop across LED
  • V = supply voltage
  • Iₒ = current across one LED

For more concepts check out to get quick answers by using this free tool.

How to Calculate Power Dissipation?

The instructions below will show you how to simply calculate the power dissipation of LEDs and resistors. Follow these guidelines and you'll have the result in a matter of seconds.

  • Step 1: Learn how LEDs are wired together in a circuit, as well as the supply voltage, the current flowing through the LED, and voltage drop.
  • Step 2: Calculate the power dissipation of a single LED and all LEDs using the formulas below.
  • Step 3: To acquire the output, substitute the values in the formula and conduct the relevant operations.

How to Use the LED Resistor Calculator?

The following is the procedure how to use the LED Resistor Calculator

  • Step 1: Fill in the appropriate input fields with the unknown's Circuit type, number of connected LEDs, supply voltage, voltage drop, current, and x.
  • Step 2: To obtain the result, select "Calculate the unknown" from the drop-down menu.
  • Step 3: Finally, the power dissipation will be displayed in the output field.

Examples of LED Resistor

Question 1: If you have one LED and wish to power it with a supply voltage of Vs = 4.8V, what current limiting resistor value should you use?


To calculate the current limiting resistor, search for the LED's specified forward voltage and forward current specifications in the datasheet (always RTFM first!). In this case, the voltage and current are 4.1V and 40mA, respectively.

Remember to convert all of your measurements to Volts, Amps, or Ohms! For example, 1mA = 0.001 Amps

When you plug the numbers into the equation above, you get R = 4.8V - 4.1V/ 0.04A = 17.5 Ohms

R = 17.5 Ohms

FAQs on LED Resistor

1. Is a resistor required for each LED?

When an electric current passes through a light-emitting diode (LED), light is emitted. If the voltage drop of the LED equals the voltage source in an electric circuit, no resistor is required.

2. How do you figure out how many resistors you'll need for an LED?

Resistor = (Battery Voltage - LED Voltage)/desired LED current is the formula for calculating the resistor. Find the resistor needed for an LED using the formula.

3. Is it possible to connect an LED without a resistor?

Almost never connect an LED to a circuit without a resistor. When connecting an LED, a current-limiting resistor should always be used to prevent the LED from the full voltage.

4. Will LEDs be brighter at a higher voltage?

Lowering or raising the voltage affects the brightness, but only because it also affects the current: a greater voltage indicates a higher current in an LED.