Resistors & Passive
LED Series Resistor Calculator
Prevent burning out LEDs by finding the exact resistance and recommended standard resistor wattage.
Input Parameters
V
V
mA
Calculation Results
Required Resistance (Ω)
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Resistor Power Dissipation (mW)
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Formula & Theory
R = \frac{V_{supply} - V_{forward}}{I_{LED}}
Frequently Asked Questions
Q: Why does an LED need a series resistor?
LEDs have non-linear forward voltage characteristics. Without a current-limiting resistor, excessive current will burn out the LED.
Q: What is standard forward voltage for blue/white LEDs?
Blue and white LEDs typically have forward voltages between 3.0V and 3.4V, while red LEDs are around 1.8V to 2.2V.