In lighting design, lumens, lux, and candela answer different questions. They are connected, but not interchangeable.

Lumen (lm): total light output

Lumen measures total visible light emitted by a source in all directions. A lamp rated around 800 lm is commonly comparable to a traditional 60 W incandescent in perceived output.

Lux (lx): light on a surface

Lux is lumens per square meter (lm/m2). It tells you how much light actually reaches a working plane. Desk tasks often target roughly 300-500 lx, while hallways can be much lower.

Candela (cd): directional intensity

Candela measures light intensity in a specific direction. Spotlights and flashlights can have high candela even if total lumens are moderate, because they focus light into a narrow beam.

  • Lumen: total emitted light
  • Lux: received light on a surface
  • Candela: directional beam intensity

For practical lighting choices, combine these units with beam angle, mounting height, and room use instead of relying on a single number.