Calculate the correct LED series resistor value using supply voltage, LED forward voltage, forward current, resistor power rating, and multiple LED configurations for safe LED circuit design.
5V Red LED
VIN = 5V, red LED = 2V, current = 20mA, quantity = 1. Resistor voltage is 3V, so resistor is 150Ω.
12V LED String
For three white LEDs at 3.6V each, total LED voltage is 10.8V. The resistor drops the remaining voltage.
This colorful SVG is an original redraw of a series LED resistor circuit. It shows supply voltage, current limiting resistor, LED voltage and LED current direction.
This LED Resistor Calculator helps calculate series resistor value, resistor power and recommended wattage for LED circuits.
LEDs are current-driven components. If an LED is connected directly to a voltage source without proper current limiting, it can draw too much current and fail quickly. A series resistor drops the extra voltage and limits current to a safe value. This calculator uses supply voltage, LED forward voltage, LED current and number of series LEDs to estimate the required resistor.
An LED needs a resistor to limit current. Without current limiting, the LED may overheat and fail.
Forward voltage is the voltage drop across the LED when it is conducting current.
Use the LED datasheet current rating. Many small indicator LEDs are commonly used around 10mA to 20mA.
Yes, but total LED voltage must stay lower than VIN so the resistor can drop the remaining voltage.
If total LED voltage is equal to or higher than VIN, there is no voltage left for the resistor to control current.
Choose the suggested wattage or a higher standard value for better safety margin.
For high-power LEDs, a constant-current driver is usually better than a simple resistor.
Yes. Different LED colors have different forward voltages, which changes resistor voltage drop.
LED Resistor Calculator is a free online calculator tool. Use it to get instant, accurate results for your electronics calculations.