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      • Published 23 Jan 2024
      • Last Modified 26 Feb 2024
    • 3 min

    LED Resistor Value Calculator

    Use our helpful LED resistor value calculator to determine what resistor value you require for your LED lighting.

    Discover the right resistor value with our LED resistor value calculator, incorporating the principles of the law of Ohms and the formula of resistance. Our user-friendly calculator helps you determine the resistance needed to power one or more series-connected LEDs from a specified voltage source at a designated current level.

    The calculation, rooted in Ohm's Law, also accounts for the voltage drop across the LED. Simply input your known values, click the calculate button, and let our tool provide the desired resistor value.

    Our LED resistor value calculator is your go-to resource for efficient and precise results, ensuring the optimal performance and longevity of your LED circuits while demystifying concepts like what is Ohm's law and how to calculate Ohm's law. Master the art of calculating resistance with insights into the colour code on resistors, current limiting resistors, and how to calculate resistance.

    LEDs (Light Emitting Diodes) are fundamental components in electronics. They are commonly used for applications including lighting, communication, and indication, to name just a few examples. However, LEDs cannot regulate current and without limited current flow, they will eventually fail. In most cases, this can be solved by adding an appropriate resistor in series with the LED.

    Resistance formula

    Resistance formula

    To calculate the resistor required for a basic LED circuit, subtract the LED's forward voltage drop from the source voltage and apply Ohm's Law.

    Utilise the formula on the left, where:

    • R represents the resistance, measured in Ohms (Ω)
    • Vs denotes the supply voltage, measured in Volts (V)
    • Vf signifies the LED's forward voltage drop, measured in Volts (V)
    • If represents the forward current through the LED and resistor, measured in Amperes (A)
    LED forward voltage table

    LED forward voltage

    LED forward voltage typically ranges between 1.8 and 3.3 Volts, varying according to LED colour. For instance, a red LED generally exhibits a voltage drop between 1.8 and 2.1 Volts. However, since both light frequency and voltage drop increase with band gap, a blue LED may have a voltage drop ranging from 3 to 3.7 Volts. Red LED forward voltage is usually at the lower end of the range scale, whereas white LED forward voltage is typically at the higher end.

    Understanding the colour code on resistors is crucial in this process. You can see the typical Vf ranges according to LED colour in the table on the right.

    Resistors and LEDs products ranges