LED in Series Calculator

Last Updated on April 10, 2024

Use LED in Series Calculator to choose the suitable Resistor Value for your LED and LEDs connected in Series Connection. Most LED devices are constant current devices with some forward voltage drop, these Forward Voltage and Forward current are decided by the semiconductor (Color) used inside the LEDs. So every LED needs forward voltage that is more than its voltage drop to allow current flow. Excess current flow may fuse the LED, hence we need current limiting Resistor connected in series with LED. As we know by controlling current flow of LED, we can control the Brightness of emitting light.

LED in Series Calculator

LED in Series Calculator

Required Series Resistor:

Resistor Value: – (Ω) ohms

Resistor Wattage: – Watts

To find the Suitable Series Resistor Value you need to know the following Input Details.

1. Input Supply Voltage in V = Applying Voltage to the circuit (Bias) in Volts,

2. LED Forward Voltage (Vf) in V = Each LED will have different Forward Voltage Range depends on its color and size, here is the typical chart for LED Forward Voltage. Refer datasheet of LED you purchase, for more accurate Vf Value.

3. LED Forward Current (If) in mA = Forward Current of Typical 5mm LED is between 20mA to 30mA, you can use these values for all color 5mm LED and the best practice is to refer datasheet.

4. Number of LEDs in Series = Count of LEDs in Series in decimal numbers. Minimum 1 and the Number of LEDs forward voltage total should not be exceed the Supply Voltage value.

Hit Calculate button after entering all required input and get the Result in ohms (Ω) and Watts.

How this LED in Series Calculator Works?

Lets start with Circuit,

One LED connected in Series with a Resistor and Supply Voltage, here you can find V, Vf, If and number of LED (1).

Here two LEDs connected in series with a Resistor and Supply Voltage, you can find V, (Vf1+Vf2) sum of forward voltage drop of two LEDs, Forward current flow If and number of LEDs (count 2).

So the formula for LED in Series calculator is written as in Java script,


V is Supply Voltage
Vf is forward voltage drop of LED (if two or more, Vf1+Vf2 .. = Vf)
N is Number of LEDs in series
If is forward current of LED (if two or more, If1+If2 .. = If)

To calculate power this calculator use the following formula,

P = I2 * R

Here, I is total If.

Types of LEDs

5mm LED
Power White LED

LEDs are comes in different Size and package, Some LED making companies provides custom size and requirement based LEDs also. LEDs and LED lighting grows exponentially and you can see countable LEDs around you (Just Look). LED Lighting Market is huge than your expectation, it is projected to reach US$ 128.15 Billion by 2030.

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