Led Resistor Pro

A practical tool for electronics hobbyists, students, and

makers who work with LEDs.

CALCULATORS

• Single LED — enter supply voltage and forward current, get the exact resistor

value snapped to E24/E12 series with 4-band and 5-band colour codes.

• Series string — calculates the single dropping resistor for any number of

LEDs in series.

• Parallel array — per-LED or shared resistor mode, shows per-branch and total

current.

• Matrix (series-parallel) — handles multi-string arrays with a resistor per

string.

• RGB LED — independent resistor for each channel (R/G/B), common-cathode or

common-anode, with a live colour preview.

CIRCUIT VIEWS

Every calculator shows an animated circuit diagram that responds to your

inputs — LED brightness scales with forward current, particles flow along

the wires.

LED LIBRARY

109 LEDs across 26 categories: standard 3/5/8/10 mm, high-brightness,

high-power (1 W – 10 W), SMD (0402 to 5730), COB modules, RGB, bicolour,

IR, UV, flashing, 7-segment, and LED strips (12 V and WS2812).

Tap any LED to view its full datasheet and open it directly in the calculator.

GRAPHS

Interactive I–V curves (Shockley model), resistor value vs supply voltage,

and resistor/LED power vs current — pinch to zoom, drag to pan.

LEARN

Ten built-in lessons covering LED basics, forward voltage, resistor selection,

colour codes, series/parallel wiring, RGB LEDs, high-power LEDs, and strips.

No ads. No internet required. Works fully offline.