Grow light coverage & PPFD calculator
Watts don't grow plants. Photons do. Wattage × efficacy gives the photon flux (PPF); spread over your canopy it becomes PPFD, and PPFD × hours becomes the daily light integral the crop actually experiences.
Fixture & coverage
Result
16 ft² (1.49 m²) canopy, 90% utilization
This assumes photons spread evenly with 90% reaching the canopy: real fixtures run hotter in the center and dimmer at the edges, and hanging height changes the map. Treat it as a shopping estimate; verify with a PAR meter or the manufacturer's PPFD chart. Above ~1000 µmol/m²/s, plants need CO₂ enrichment to use the extra light.
Every one of those watts becomes heat: size the cooling → or the power bill →
What PPFD do you need for hydroponic growing?
Target roughly 200-400 μmol/m²/s PPFD for vegetative growth and 600-900+ for flowering, though exact targets depend on crop and CO2 level. PPFD comes from your fixture's wattage and efficacy (μmol/J) spread over your coverage area, and DLI (daily light integral) multiplies that by photoperiod. Enter your fixture and coverage area above to check both against stage targets.