Photometry Tools
Watts to Lux Calculator
Calculate surface illuminance in lux (lx) produced by electrical wattage power (W) over a specified coverage area.
Calculation Input
Illuminance Density
0.00 lx
Total Emitted Luminous Flux
0.00 lm
Heat Emission Ratio
Low Heat (10%)
Converting Watts to surface Lux
To find the target surface illuminance in lux ($lx$) produced by electrical wattage power, first multiply the watts by the bulb efficacy ($\eta$, lm/W) to get overall light flux in lumens. Then divide lumens by surface area in square meters:
$$E_{lx} = \frac{P_W \times \eta}{A_{m^2}}$$
Where $\eta$ is the light bulb efficacy. For example, a 10W LED with 90 lm/W efficacy generates 900 lm, producing 45 lx over a 20 m² area.