LED series & parallel resistor calculator
Wiring several LEDs to one supply? Choose series, parallel or a series-parallel array and this calculator finds the resistor for every string, the total current draw and the power, then draws the wiring for you.
Enter your values
Wiring lots of LEDs? Put them in a series string, in parallel branches, or both (a series-parallel array). Get the resistor for every string, the total current and the power.
Resistors for the parallel LEDs
Result
Series: R = (Vs − N × Vf) ÷ IfParallel, one R per LED: R = (Vs − Vf) ÷ IfSeries-parallel, one R per string: R = (Vs − M × Vf) ÷ IfTotal current = strings × If · P = I² × RCoro's tip: Series is the most efficient: one resistor, the same current through every LED. When the supply can't push enough volts for one long string, split the LEDs into shorter strings in parallel — and give every string its own resistor. Leave at least 1 V for each resistor.
LED series & parallel resistor calculator: common questions
Is it better to wire LEDs in series or parallel?
Series is more efficient: one resistor and the same current through every LED. Use parallel strings only when the supply voltage is too low for one long string.
Can parallel LEDs share one resistor?
It is not recommended. Small differences in forward voltage make one LED take more current than the others. Give each LED or each string its own resistor.
How many LEDs can I put in series?
The total forward voltage must stay below the supply, leaving at least about 1 V across the resistor. For example, a 12 V supply can run four 2 V red LEDs in one string.
For learning and low-voltage hobby circuits (12 V and below). Always check the part's datasheet. Never use these tools to plan mains (230 V) wiring.