LED Series/Parallel Array Calculator

When wiring multiple LEDs, getting the resistor and layout wrong can burn out your components — the LED Series/Parallel Array Calculator works out the correct current limiting resistor and optimal wiring layout for your LED array. Enter your power supply voltage, LED forward voltage drop, LED forward current rating, and number of LEDs, then select a preferred configuration (optimal, series, or parallel) to get the resistor value, LEDs per series branch, parallel branches, resistor power dissipation, total array power, and power efficiency.

V

DC voltage from your power source

V

Voltage drop across each LED (check datasheet)

mA

Maximum safe current for each LED

Total LEDs in your array

Results

Current Limiting Resistor

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LEDs per Series Branch

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Parallel Branches

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Resistor Power Dissipation

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Total Array Power

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Power Efficiency

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Frequently Asked Questions

What is the difference between series and parallel LED wiring?

Series wiring connects LEDs end-to-end in a single path, sharing the same current but adding voltages. Parallel wiring connects all positive terminals together and all negative terminals together, sharing voltage but adding currents. Series uses less current but requires higher voltage, while parallel uses lower voltage but higher current.

How do I determine my LED's forward voltage and current?

Check your LED's datasheet or packaging for the forward voltage (Vf) and forward current (If) ratings. Common values are 2.0-2.2V for red/yellow LEDs, 3.0-3.4V for green LEDs, and 3.2-3.6V for blue/white LEDs. Current ratings typically range from 10-30mA for standard LEDs.

Why do I need current limiting resistors with LEDs?

LEDs have very low internal resistance and will draw excessive current if connected directly to a voltage source, causing them to burn out instantly. Current limiting resistors control the current flow to keep it within the LED's safe operating range.

What happens if one LED fails in a series circuit?

In a series circuit, if one LED fails open (burns out), the entire string stops working because the current path is broken. This is why mixed series-parallel configurations are often preferred for reliability - they provide redundancy.

How do I choose the right resistor wattage?

The resistor must handle the power it dissipates as heat. Use a resistor rated at least 2x the calculated power dissipation for safety. For example, if the calculator shows 0.25W dissipation, use at least a 0.5W resistor.

What is the optimal LED array configuration?

The optimal configuration maximizes efficiency by minimizing resistor power loss while maintaining reliability. It typically involves putting as many LEDs in series as the supply voltage allows, then using parallel branches for the remaining LEDs.

Can I mix different colored LEDs in the same array?

Only if they have the same forward voltage and current ratings. Different colored LEDs usually have different electrical characteristics, so they should be calculated and wired separately to ensure proper current distribution.

What supply voltage should I use for my LED array?

Choose a supply voltage that allows for efficient series connection of multiple LEDs. A good rule is: supply voltage should be at least 2V higher than the total forward voltage of LEDs in series to allow for proper resistor operation and voltage regulation.