PPFD converter
Convert grow light intensity between PPFD, lux and watts per square meter, and work out the daily light integral.
That's 1.33× as bright as seedlings under lights, while a flowering crop is 2× brighter. Over a 12-hour day that is a light integral of about 17.28 mol/m².
What it means
How much light is that?
Lux and PPFD relate differently for every light source, because lux weights by the human eye. The 54 lux per µmol used here is the daylight figure; a red-heavy LED can be half that.
Every unit
Your light level in every unit
Learn
Three things worth knowing
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DLI = PPFD × hours × 0.0036
400 µmol/m²/s for 12 hours is a daily light integral of 17 mol/m²/day, which suits most flowering houseplants.
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Why moles of photons
Photosynthesis is a photon-by-photon process: roughly ten photons fix one molecule of CO₂. Counting photons rather than energy measures what the plant can actually use.
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Lux tells you little
Two lamps reading the same lux can differ twofold in PPFD if one is a warm white LED and the other a purple blurple. Convert only when you know the spectrum.
Shortcuts
Popular light level conversions
Background
About PPFD and PAR
Plants count photons between 400 and 700 nm — photosynthetically active radiation — and PPFD measures how many land on a square meter each second, in micromoles.
Lux is the wrong unit for plants: it weights light by the human eye, which peaks in the green that chlorophyll reflects. A lux meter flatters green light and undercounts the red and blue that plants actually use.