Work backward from a measured illuminance and distance to a light source's actual luminous intensity in candela.
How to Use the Lux to Candela Calculator
Type in the illuminance your light meter reads, in lux, and the distance in meters between the meter and the source. Luminous intensity in candela recalculates on every keystroke.
Datasheets and product boxes love a big candela number, but it's rarely something you can check directly — that would take a calibrated integrating sphere pointed at the source itself. What you actually have, standing in a room with a light meter, is an illuminance reading at some known distance. The inverse-square law lets you work backward from that to the source's real intensity.
cd = lux × distance²Illuminance falls off with the square of distance, so reversing the relationship means multiplying instead of dividing: double the distance and the same lux reading implies four times the candela. Take the defaults here — 55.6 lux measured 3 meters out — and the source works out to just over 500 candela, a fairly modest household spotlight. This is the calculation an electrician or stage lighting tech runs when a flashlight or spotlight claims "50,000 candela" on the box and they want to check that against a meter reading, rather than just trusting the marketing copy.
One thing worth flagging: this only holds for a point source, or something close enough to one — a bare LED, a small reflector bulb, a spotlight beam measured well beyond its own physical size. Measure too close to a large diffuse panel and the inverse-square law breaks down, because the source no longer behaves like a single point.