Estimate the area a grow light covers at a light target.
A fixture's photon output is watts times its efficiency, and dividing that by the target light level gives the area it can cover. Matching fixture size to bench area prevents weak, leggy plants from underexposure while avoiding overbuying light and electricity.
Grow Light Coverage
Coverage = (watts x efficiency) ÷ target PPFD
Coverage = (watts x efficiency) ÷ target PPFD A fixture's photon output is watts times its efficiency, and dividing that by the target light level gives the area it can cover.
Matching fixture size to bench area prevents weak, leggy plants from underexposure while avoiding overbuying light and electricity.
This calculator takes 3 inputs: Fixture watts, Efficiency, Target PPFD. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.