Lux
A measure of illuminance — how many lumens hit one square meter of surface. Used to specify lighting levels for rooms and workspaces.
Lumens tell you how much light a bulb produces. Lux tells you how much of that light actually arrives at the surface where you need it. A 1000-lumen bulb high up in a vaulted ceiling delivers far fewer lux at desk level than the same bulb in a table lamp two feet away.
Lux is the measurement that lighting designers and building codes use because it accounts for distance, beam angle, and room geometry. Office standards typically require 300-500 lux on the work surface. A cozy living room might be 150 lux. A surgery room needs 1000+ lux.
You can measure lux with a smartphone app or a dedicated lux meter. It's a useful sanity check when your room feels too dim or too bright — rather than guessing whether you need more or fewer lumens, measure the lux at the surface and compare to recommended levels.
Specifications
| 150 lux | Living room / bedroom |
| 300 lux | Office / kitchen general |
| 500 lux | Detailed task work |
| 1000+ lux | Surgery / precision work |
Related Terms
- Lumens
The unit measuring total visible light output. Unlike watts, lumens tell you how bright a bulb actually is.
- Foot Candle
A measure of illuminance in imperial units — one lumen per square foot. Commonly used in US building codes and lighting design.
Mentioned in
Can A Lux Meter Measure LED Light?
Standard lux meters work on LED light — but with a calibration error that can be off by a factor of 10 or more for saturated colored LEDs. That spectral mismatch is exactly why an LED-specific meter exists.
What Is The Difference Between Lumen And Lux?
Double the distance from a bulb and lux doesn't halve — it drops to one quarter. That inverse square law is exactly why lumens on the box and brightness in the room rarely tell the same story.
Do Pond Lights Affect Fish?
Even 1 lux of artificial light at night — about the brightness of a single candle — is enough to suppress melatonin and throw a fish's circadian rhythm off. A timer fixes most of that in one step.
Are Floor Lamps Safe For Children?
Even modest light levels as low as 5 lux can suppress an infant's melatonin — which makes the floor lamp in the corner more consequential than it looks.
Can LED Lights Fade Artwork?
Van Gogh's Sunflowers now hang under LEDs at just 50 lux — not despite LED blue light, but because of it. The museum chose LEDs precisely to limit the wavelengths driving the damage.
What Is A Foot Candle Measurement?
Double the distance between a bulb and a surface, and illuminance drops to one-quarter — not one-half. That gap between lumens (what the bulb produces) and foot-candles (what actually lands on your desk) is why brighter bulbs don't always fix dim rooms.