About

When retrofitting lighting systems, converting Watts to Lumens is necessary to maintain consistent brightness while reducing energy load. Watts measure power consumption, while Lumens measure visible light output. The ratio between them is "Luminous Efficacy" (lm/W), which varies drastically between technologies. A standard incandescent bulb converts most energy into heat, achieving low efficacy, whereas modern LEDs convert significantly more energy into visible light.

This tool utilizes a database of standard efficacy ranges to estimate light output. Accurately matching Lumens is critical in architectural lighting and workplace safety to ensure adequate lux levels are maintained when upgrading to energy-efficient fixtures. Direct conversion is impossible without specifying the technology type, as a 10W LED produces vastly more light than a 10W incandescent bulb.

Formulas

The calculation of luminous flux requires the specific efficacy of the light source:

Φ_v = P × η

Where Φ_v is the luminous flux in Lumens (lm), P is power in Watts (W), and η (eta) is the luminous efficacy in Lumens per Watt (lm/W).

Reference Data

Technology	Efficacy (lm/W)	100W Equivalent Output	Lifespan (Avg)
Incandescent (Standard)	15 lm/W	1500 lm	1,000 hrs
Halogen	20 lm/W	2000 lm	2,500 hrs
CFL (Compact Fluorescent)	60 lm/W	6000 lm	8,000 hrs
LED (Standard)	90 lm/W	9000 lm	25,000 hrs
LED (High Efficiency)	120 lm/W	12000 lm	50,000 hrs
Metal Halide	85 lm/W	8500 lm	15,000 hrs
High Pressure Sodium	100 lm/W	10000 lm	24,000 hrs
Low Pressure Sodium	150 lm/W	15000 lm	18,000 hrs

Frequently Asked Questions

Luminous efficacy is the ratio of luminous flux (light output) to power (electricity input). It measures how well a light source produces visible light. Higher numbers mean more light for less electricity.

A standard 60W incandescent bulb produces approximately 800 Lumens. To replace it, you need an LED bulb rated for 800 Lumens, which typically consumes only 8 to 10 Watts.

LED technology is rapidly evolving. Early LEDs produced 50-70 lm/W. Standard consumer LEDs now average 80-100 lm/W, while high-end industrial or laboratory LEDs can exceed 150-200 lm/W.

Slightly. Cool white LEDs (5000K+) often have slightly higher efficacy than Warm white LEDs (2700K) because the phosphors used to create warm light absorb a small amount of the output.