Photometry Tools
Watts to Lumens Calculator
Calculate total visible output luminous flux in lumens (lm) from electrical power in watts (W).
Calculation Input
Luminous Output Flux
0.00 lm
Bulb Source Efficiency Tier
High Efficiency LED
Heat Emission Ratio
Low Heat (10%)
How Watts relate to Lumens
Visible light output in lumens ($lm$) is calculated by multiplying electrical power consumption in watts ($W$) by the bulb luminous efficacy ($\eta$, lumens per watt):
$$lm = W \times \eta$$
Where $\eta$ is the light bulb efficacy. For example, a 10W LED with 90 lm/W efficacy generates 900 lumens of light flux.