Units & Conversion · 流明与勒克斯（Lumen & Lux） · Updated 2026-10-25
What Is Lumen & Lux?
Definition
Lumens quantify total visible light emitted (the modern replacement for watts: a 9W LED ≈ a 60W incandescent ≈ 800 lm); lux quantifies illumination per area = lm/m². The same lamp yields lower lux in a big room — so design by target lux: living rooms 100-300 lx, desks 500 lx, precision work 1000 lx, corridors 50-100 lx. A 1,000 lm bulb over 20 m² averages just 50 lx; multi-source layouts are mandatory.
Formula
E(lx) = Φ(lm) / A(m²), derated by a utilization factor of 0.4-0.6
Worked Example
A 15 m² study at 500 lx needs 500×15 = 7,500 lm arriving; at a 0.5 utilization factor, install ~15,000 lm total (≈150W of LED, split across fittings).
Common Misconception
"Watts mean brightness" — LED efficacy varies 3× at the same watts; read lumens. And "high lumens light up the room" — area and beam angle decide: a 1,000 lm spotlight delivers 300 lx on the desk and far less on the wall.
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