How the lux ↔ footcandle conversion works
A footcandle is defined as one lumen per square foot, while a lux is one lumen per square meter. Since 1 foot equals exactly 0.3048 meters, one footcandle equals a fixed number of lux.
- lx — lux — lumens per square meter (SI)
- fc — footcandle — lumens per square foot (imperial)
- 0.3048 m — exact length of 1 foot (1959 international yard-and-pound agreement)
More detail
Where each unit is used
Lux is the SI unit and the standard in international and Korean (KS) lighting specifications. Footcandles remain common in North American lighting standards published by the IES (Illuminating Engineering Society), so imported light meters and US-sourced fixture datasheets often list output in fc instead of lx.
Typical illuminance levels
Full moonlight is roughly 0.1–1 lx, an overcast outdoor day is around 1,000 lx (~93 fc), and typical office lighting sits near 300–500 lx (~28–46 fc). Direct sunlight can exceed 32,000 lx (~2,970 fc).
Practical tip. If a US-made light meter or datasheet reports footcandles, multiply by ~10.76 to get lux for comparison against KS-spec lighting requirements — the converter above does this exactly.
Frequently asked questions
How many footcandles is 500 lux?
500 lx ≈ 46.4515 fc, since 1 fc = 10.76391 lx. Enter 500 with "Lux → Footcandle" selected above to see the precise conversion.
How many lux is 1 footcandle?
1 fc = 1 lm/ft² and 1 ft = 0.3048 m exactly, so 1 fc = 1/(0.3048)² lx ≈ 10.7639104167 lx, normally written as ≈10.76391 lx.
How many lux is 100 footcandles?
100 fc ≈ 1,076.39 lx (100 × 10.76391). Select "Footcandle → Lux" above and enter 100 to confirm.
Why do lux and footcandle both appear in lighting specs?
Lux is the SI unit used worldwide, including Korean (KS) standards, while footcandle is the legacy imperial unit still used in North American IES lighting tables — this converter bridges the two for imported fixtures or meters.