LED Resistor Calculator - Optimize Your Circuit Design


The LED Resistor Calculator is a tool that simplifies the process of determining the value of the resistor needed to safely connect an LED or a series/parallel network of LEDs to a power source. LEDs, or Light Emitting Diodes, are semiconductors that emit light when an electric current passes through them. However, without a resistor, the LED can draw too much current, potentially damaging the LED or even causing a safety hazard.

This calculator automates the complex equations related to Ohm's law and the power law to help you find the required resistor value, taking into account the specific properties of your LEDs and the characteristics of your power source.


You can use this tool whenever you want to connect one or multiple LEDs to a power source and you need to calculate the value of the current-limiting resistor that should be used. It is especially handy when dealing with multiple LEDs in series or parallel, as these configurations can be difficult to calculate manually.


  1. Medium (LEDs connected in Series or Parallel): LEDs can be connected in a circuit in two primary ways – in series, where the LEDs are linked end-to-end in a single line, or in parallel, where the LEDs are all directly connected to the power source. The choice of medium impacts how voltage and current are distributed across the LEDs.

  2. Number of connected LEDs: This refers to the total quantity of LEDs connected in the circuit.

  3. Supply voltage (V): The voltage provided by the power source in your circuit.

  4. Current through the LED (mA): The amount of electric current that you want to pass through each LED, usually specified by the LED manufacturer.

  5. LED color: The color of the LED can sometimes influence the voltage drop across it, with different colors corresponding to different semiconductor materials with varying properties.

  6. Voltage drop across LED (V): The amount of voltage "used" by each LED. This value, typically provided by the LED manufacturer, depends on the type and color of the LED.

  7. Resistance (Ω): The resistance that needs to be added to the circuit to ensure that the correct amount of current flows through the LEDs. This is what the calculator helps to determine.

  8. Power dissipation: The power dissipated (given off as heat) by the LEDs and the resistor. Power dissipation is important to consider because electronic components can be damaged if they get too hot.

    • In a single LED (MW): The power dissipated by a single LED in the circuit.

    • In all LEDs (MW): The total power dissipated by all the LEDs in the circuit.

    • In the resistor (MW): The power dissipated by the resistor in the circuit.

Related Math Equations

The tool primarily uses Ohm's Law and the Power Law to calculate the required resistance and power dissipation. These laws are expressed as:

  1. Ohm's Law: V = I * R, where V is voltage (volts), I is current (amps), and R is resistance (ohms). This law is used to calculate the required resistance in the circuit.

  2. Power Law: P = I * V, where P is power (watts), I is current (amps), and V is voltage (volts). This law is used to calculate the power dissipation in the LEDs and resistor.

For a series circuit, the supply voltage is the sum of the voltage drops across each LED and the resistor. For a parallel circuit, the supply voltage equals the voltage drop across each LED (assuming they are identical).


It is believed that these calculations are accurate, but not guaranteed. Use at your own risk!