084 - Lighting Calculations: How Many Fixtures Does a Room Need?

A lighting calculation is multiplication and division, not engineering math. This episode covers the foot candle chart, the lumen method formula, and the inverse square law.

Most candidates skip lighting calculations because the phrase sounds harder than the work actually is. The arithmetic was never the problem. The vocabulary was.

Layla walks through recommended foot candle levels by space type, then runs two complete fixture-count calculations with every step showing. You will see what happens to the answer when dark finishes and skipped maintenance enter the equation. There is a free 10-question comprehension quiz at the bottom of the blog post to check what stuck.

📝 Key topics covered:

Foot candle chart: recommended light levels by space type

Lumen method formula: calculating fixture count for a room

Coefficient of utilization: how much light reaches the work surface

Light loss factor: lamp lumen depreciation and luminaire dirt depreciation

Inverse square law: double the distance, quarter the light

Lumens per lamp versus lumens per fixture

⏱️ Chapters:

(0:00) Lighting Calculations