Calculate daily light integral (DLI) from photosynthetic photon flux density (PPFD) and photoperiod.
| DLI (mol/m²/day) | – |
Use this calculator to estimate how much photosynthetically useful light a plant receives in a day. Growers track DLI to see whether seedlings, herbs, or a greenhouse crop are under- or over-lit. PPFD is the instantaneous useful intensity at the canopy; photoperiod is how long that light stays on.
DLI in mol/m²/day is PPFD in µmol/m²/s × hours × 0.0036. The factor 0.0036 converts micromoles per second over those hours into moles per square metre per day (3600 seconds per hour ÷ 1 000 000 µmol per mol). The calculation assumes PPFD stays constant over the photoperiod. Real sunlight and dimmable LEDs vary; this is the square-wave version.
PPFD (µmol/m²/s): Photosynthetic photon flux density at the leaves, from a quantum meter or the fixture chart.
Photoperiod (h): How many hours the lights (or equivalent sun) stay on in a day.
DLI (mol/m²/day): Daily light integral, the total photosynthetic photon dose over 24 hours.
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