LED Resistor Calculator
Calculate the resistor needed for an LED circuit.
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mA
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Frequently Asked Questions
What is a typical LED forward voltage? +
Red LEDs typically have a forward voltage of 1.8-2.2V, green and yellow around 2.0-2.4V, blue and white around 3.0-3.6V. Always check the datasheet for your specific LED, as values can vary.
Why do I need a resistor with an LED? +
LEDs have very low internal resistance, so without a current-limiting resistor, they draw excessive current and burn out instantly. The resistor drops the extra voltage and limits current to a safe level.
What are E24 standard resistor values? +
The E24 series has 24 values per decade (1-10 ohms, 10-100 ohms, etc.) with 5% tolerance. Common values include 100, 150, 220, 330, 470, 680, 1k, 1.5k, 2.2k, 3.3k, 4.7k, and 6.8k ohms.
What happens if I use a larger resistor than calculated? +
A larger resistor reduces the current, making the LED dimmer but safer. It is always better to round up to the next standard value. Using a much larger resistor will make the LED very dim or not light up at all.
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