Why These Three Numbers Define Every Lighting Project
Whether you're specifying lighting for a corporate headquarters or a logistics warehouse, three numbers will define the quality and performance of your installation: lumens, lux, and CRI. Understanding the difference — and how they interact — is the foundation of professional lighting design.
Lumens: The Output of the Luminaire
Lumens (lm) measure the total amount of visible light emitted by a light source. A higher lumen output means a brighter luminaire. However, lumens alone don't tell you how bright a space will feel — that depends on how the light is distributed across the room.
- A typical office LED panel: 3,000–5,000 lm
- A high-bay warehouse luminaire: 15,000–50,000 lm
- A street light: 8,000–20,000 lm
Lux: The Light That Reaches the Surface
Lux (lx) measures illuminance — the amount of light falling on a surface per square metre. This is what actually matters for the people working in the space. The formula is simple:
Lux = Lumens ÷ Area (m²)
International standard EN 12464-1 defines recommended lux levels for different tasks:
| Application | Recommended Lux |
|---|---|
| Office (general) | 500 lx |
| Warehouse (picking) | 300 lx |
| Retail (general) | 500–750 lx |
| Manufacturing (precision) | 750–1,000 lx |
| Corridor / Circulation | 100–200 lx |
CRI: The Quality of the Light
Color Rendering Index (CRI) measures how accurately a light source renders colors compared to natural daylight (CRI 100). It's rated on a scale of 0–100.
- CRI ≥ 80: Suitable for most commercial applications
- CRI ≥ 90: Recommended for retail, healthcare, and color-critical tasks
- CRI ≥ 95: Required for color inspection, art galleries, and premium retail
Putting It All Together
When specifying a commercial lighting project, always define your target lux level first (based on the task), then select luminaires with sufficient lumen output to achieve it, and finally choose a CRI appropriate for the application. This three-step approach ensures both energy efficiency and visual comfort.
Need help calculating the right specification for your project? Use our Lighting Tools Library or contact our technical team.