Enter your Supply Voltage, LED Forward Voltage, LED Current, and Number of LEDs into the LED Resistor Calculator to find the right Resistor Value, Power Rating, Voltage Drop, and Voltage Across Resistor so your LEDs shine safely.
Resistor Value
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Minimum Resistor Power
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Recommended Resistor Power
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Total LED Voltage Drop
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Voltage Across Resistor
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A current-limiting resistor prevents excessive current from flowing through an LED, which could damage or destroy it. LEDs have very low resistance and would draw too much current without a resistor to limit the flow.
Forward voltage depends on LED color and type. Typical values are 1.9-2.1V for red/orange/yellow LEDs, 3.1-3.5V for blue/white/green LEDs, and 1.2V for infrared LEDs. Check your LED datasheet for exact values.
Choose a resistor with a power rating 2-10 times higher than the calculated minimum power to ensure reliable operation and prevent overheating. Higher safety factors provide better long-term reliability.
Yes, this calculator works for LEDs connected in series. For parallel LEDs, each branch needs its own current-limiting resistor. The calculator assumes all LEDs are identical and connected in series.
If the supply voltage is lower than the total LED forward voltage, the LEDs won't turn on or will be very dim. Ensure your supply voltage is at least 1-2V higher than the total LED voltage drop.
Resistors generate heat when current flows through them. Using a higher power rating than calculated ensures the resistor operates well below its maximum temperature, improving reliability and lifespan.
Supply voltage is your power source voltage (battery, power supply). Forward voltage is the voltage drop across each LED when current flows through it. The resistor drops the remaining voltage.