LED Array Calculator
Design a series-parallel LED array — get resistor value per branch, total current and power.
Resistor per branch
300 Ω
E12: 270 Ω
Total current
44.4 mA
Total power
533 mW
Formula
Vsupply > Vforward × (LEDs in series)
Each parallel branch gets its own current-limiting resistor.
Driving many LEDs
To light more than one LED, put several in series within a branch (their forward voltages add) and run several branches in parallel. The layout above mirrors your series × parallel settings.
Give every branch its own resistor rather than one shared resistor — small differences between LEDs otherwise make current sharing uneven and some run hot.
Design notes
- Series LEDs per branch are limited by the supply: you need headroom above the summed forward voltage for the resistor.
- Total current = branch current × number of branches — check your supply can deliver it.
- For large arrays or strips, a constant-current driver beats simple resistors for efficiency and brightness matching.
Where it's used
LED matrices and signage, indicator banks, backlights, and decorative or grow-light panels.
Frequently Asked Questions
How many LEDs can I put in series?+
As many as the supply voltage allows: LEDs in series × forward voltage must be less than the supply voltage (leaving ~1–2 V for the resistor).
Why use parallel branches?+
Parallel branches increase total brightness (more LEDs, more current) without requiring a higher supply voltage. Each branch gets its own current-limiting resistor.