What is a Lumen?

Lumens vs Watts

Traditionally, lighting was specified by wattage — a 100W incandescent bulb was 'brighter' than a 60W bulb. But wattage measures electrical power consumption, not light output. Two LED luminaires consuming the same wattage can produce vastly different lumen outputs depending on LED chip efficiency, driver quality and optical design.

Lumens measure what actually matters: how much light reaches the space. A modern LED downlight might produce 1,200 lumens from just 12 watts, whereas an old halogen lamp needed 50 watts for the same output. This is why lumens have replaced watts as the primary specification metric for commercial LED lighting.

How Many Lumens Do I Need?

The lumen output you need depends on the application and the required lux level (lumens per square metre). As a rough guide:

• Office workspace — 400–500 lux → typically 3,000–4,500 luminaire lumens per fitting in a standard 600×600 grid • Corridor — 100–150 lux → lower lumen fittings spaced further apart • Retail — 300–500 lux → higher output with good colour rendering • Warehouse — 150–300 lux → high-bay luminaires producing 15,000–30,000 lumens per fitting • Classroom — 300–500 lux → uniform distribution across desk height

Always refer to CIBSE SLL lighting guides and BS EN 12464-1 for the applicable maintained illuminance values for your project type.

Luminaire Lumens vs Lamp Lumens

When specifying LED luminaires, always check whether the quoted lumen figure is 'luminaire lumens' (light output from the complete fitting) or 'source lumens' (bare LED chip output before optical losses). Luminaire lumens account for losses in the diffuser, reflector and housing — giving a more accurate picture of usable light. At EOS, all product datasheets quote luminaire lumens as standard, ensuring transparency for specifiers.

Efficacy: Lumens per Watt

Luminous efficacy (lm/W) measures how efficiently a luminaire converts electrical power into visible light. Higher efficacy means more light for less energy. Modern commercial LED luminaires typically achieve 100–160 lm/W. EOS products are engineered to deliver market-leading efficacy without compromising colour quality, glare control or longevity.