LED Resistor Calculator
Single LED Resistor
R = (Vs - Vf) / If
LEDs in Series
R = (Vs - n × Vf) / If
Formula
R = (Vs - Vf) / If | For series LEDs: R = (Vs - n × Vf) / If
Frequently Asked Questions
How do I calculate the resistor for an LED?
Use R = (Vs - Vf) / If, where Vs is supply voltage, Vf is the LED forward voltage, and If is the desired LED current. For a typical red LED (Vf=2V, If=20mA) on 5V supply: R = (5 - 2) / 0.02 = 150 Ohms.
What is the typical forward voltage for different LED colors?
Red: 1.8-2.2V, Orange: 2.0-2.2V, Yellow: 2.0-2.2V, Green: 2.0-3.5V, Blue: 3.0-3.5V, White: 3.0-3.5V. Always check the LED datasheet.
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