Convert a lux illuminance reading into footcandles, the imperial unit older US lighting codes still specify.
How to Use the Lux to Footcandles Calculator
Enter an illuminance value in lux. The footcandle equivalent appears immediately below.
Lux is the SI unit almost every modern light meter and international manufacturer's spec sheet reports in. Footcandles are the older imperial equivalent, and they haven't gone away — US building codes, older fixture datasheets, and a lot of American lighting-design software still spec illuminance targets in footcandles even when the fixture itself was tested and rated in lux by an overseas manufacturer. That mismatch is the actual reason this conversion gets used, not academic curiosity: it bridges a spec sheet in one unit against a code requirement in the other.
fc = lux ÷ 10.764The constant comes from the ratio between a square meter and a square foot — a square foot is 1/10.764 of a square meter, and a footcandle is the illuminance from one lumen spread over that smaller area. A 500 lux reading, the kind you'd want for detailed office work, comes out to roughly 46.5 footcandles. A retail floor code calling for 30 footcandles, for comparison, translates to about 323 lux — worth working out before ordering fixtures spec'd purely in the metric unit.
Keep an eye on which unit a code actually specifies before comparing numbers — a 50 fc requirement and a 50 lux reading look interchangeable at a glance but differ by more than tenfold, an easy mistake when skimming two datasheets side by side.