Convert an indicator LED's millicandela rating and beam angle into its total luminous flux in lumens.
How to Use the Millicandela to Lumens Calculator
Enter the intensity in millicandela straight off the datasheet, then the beam angle in degrees. Candela, solid angle, and total lumens all update together.
Millicandela shows up almost exclusively on small indicator LEDs — the power light on a router, a status LED on a PCB, a tiny SMD part rated "800 mcd @ 20mA." Manufacturers rate these in millicandela because what they're actually selling is directional brightness at a specific viewing angle, not total light output. Total lumens barely matters for a part whose entire job is to be visible from roughly one direction.
cd = mcd ÷ 1000
solid angle = 2π × (1 − cos(beam angle ÷ 2))
lm = cd × solid angleThe middle step is the same beam-geometry math behind any candela-to-lumens conversion: a narrower beam concentrates the same intensity into a smaller solid angle, so widening the beam angle while holding candela fixed increases the lumen result. A 3,000 mcd LED at a tight 30° beam produces only about 0.64 lumens total. Widen that to a 120° wide-angle lens instead, same 3,000 mcd rating, and the output jumps to roughly 9.4 lumens — over ten times more, from geometry alone, with the intensity number never changing.
Where this conversion earns its keep is comparing across product categories that don't share a rating convention — sizing up a small LED's real total output against a lumens-rated bulb, say, to gauge relative brightness rather than just relative directional intensity. Outside that kind of comparison, most people working with indicator LEDs never need to touch this calculator at all.