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LED Resistor Calculator

Choose a unit
Choose a unit
Choose a unit
Choose a unit
Choose a unit

About LED Resistor Calculator

Resistors are used in series with LEDs to protect LEDs by limiting the amount of current that goes through them. While not incredibly efficient, it’s a simple, inexpensive way to reduce the chance of running too much current through your LED and either destroying it or reducing its lifespan. When calculating the resistor size that you need to use, you need to find your source voltage, the forward voltage of the LED (basically, at which point the LED starts conducting), and then how much current you want it to conduct. Then you simply subtract the forward voltage from the source voltage and divide that result by the desired current. Knowing how to do this manually is best for understanding what’s going on conceptually, but if you want to verify your work or you need to save some time, we made this calculator to make life easier for you!

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