Photometry Tools
Lumens to Watts Calculator
Calculate estimated electrical power consumption in watts (W) from total luminous flux output in lumens (lm).
Calculation Input
Estimated Power Usage
0.00 W
Bulb Source Efficiency Tier
High Efficiency LED
Heat Emission Ratio
Low Heat (10%)
Luminous Efficacy vs Power
Watts measures electrical energy consumption, while lumens measures the actual visible light output. The ratio between them is called luminous efficacy ($\eta$, measured in lumens per watt). Higher efficacy values mean more light is generated for less electricity:
$$W = \frac{lm}{\eta}$$
Where $\eta$ is the light bulb efficacy. For example, a 900 lm output requires 60W for standard incandescent (15 lm/W) but only 10W for high efficiency LED (90 lm/W).