In short
A plain-English guide to the numbers on a linear LED datasheet: lumens, watts, efficacy, CCT, CRI, UGR, IP rating, lifetime and dimming.
Linear LED datasheets are full of numbers. Knowing which ones matter makes comparing products and checking a specification much faster.
| Value | What it means | What to look for |
|---|---|---|
| Lumens (lm) | Total light output | Delivered output of the luminaire, not the LED chip |
| Watts (W) | Power consumption | System watts, including the driver |
| Efficacy (lm/W) | Efficiency | Higher is better |
| CCT (K) | Colour temperature | 2700K–4000K for most interiors |
| CRI (Ra) | Colour rendering | 80+ offices, 90+ design-led spaces |
| UGR | Glare | ≤19 for offices (check the room calculation) |
| IP rating | Dust and water protection | IP20 dry interiors, IP44+ damp areas |
| Lifetime (L80/L70) | Hours until output falls to 80% / 70% | Compare at the same condition |
| Dimming | Control protocol | DALI, Casambi, 1–10V, switch-dim |
Watch out for
- Chip lumens quoted instead of luminaire lumens
- UGR quoted for a standard room, not yours
- Lifetime quoted without the L and B values
We can compare datasheets for you. See specifier support.
Further reading at 299 Lighting
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Start a project →Frequently asked questions
What is the most important number on a linear LED datasheet?
Delivered luminaire lumens and system watts, which give the real efficacy. Then check CRI, CCT and UGR for your application.
What is the difference between chip lumens and luminaire lumens?
Chip lumens are the raw LED output. Luminaire lumens are what actually leaves the fitting after optical and thermal losses, which is the figure that matters.
