Enter a small light source's luminous flux and beam angle to calculate its luminous intensity in millicandela.
How to Use the Lumens to Millicandela Calculator
Enter the LED's lumens rating into Luminous Flux and its beam spread into Beam Angle — indicator LEDs run narrower beams than general room lighting, so the default here is 30° rather than the wider defaults used elsewhere in this category.
Millicandela exists because candela gets awkward at small-LED scale.
solid angle (sr) = 2π × (1 − cos(θ ÷ 2))
millicandela = (lumens ÷ solid angle) × 1000Why Not Just Use Candela With More Decimal Places?
A tiny status LED — the power light on a router, the activity light on a keyboard — might only produce an intensity of 0.02 cd. That's a real, usable number, but it reads as an awkward string of leading zeros on a datasheet. Multiply by 1,000 and it becomes 20 mcd: the exact same physical quantity, expressed at a scale that doesn't force every cell in a spec table to carry three unnecessary zeros.
The calculator's own defaults show the scale in action: a 20 lm LED focused into a narrow 30° beam works out to roughly 93,400 mcd — a figure that would read as a fussy 93.4 cd written the larger unit's way, and this is precisely the range small LED datasheets are built around.
It's purely a labeling convenience — millicandela isn't a different kind of measurement, just candela scaled the same way milliamps scale amps. Manufacturers of small indicator and signal LEDs settled on it because their products almost always land somewhere in the single-to-low-triple-digit mcd range, a far more readable place to live than 0.001–0.3 cd.