Daily Light Integral

DLI: Daily Light Integral mol/m²d

Daily light integral (DLI) describes the number of photosynthetically active photons (individual particles of light in the 400-700 nm range, PAR) that are delivered to a specific area over a 24-hour period. This variable is particularly useful to describe the light environment of plants.

Source: Wikipedia - DLI

More about PAR

One day with LED grow lights

DLI for the standard illumination periods 12h, short day and 18h, long day. The sample below shows a constant DLI of 26 mol/d for a short day plant (*sdp) . This is achieved by an intensity of 400 μmol/m²s for 18 hours in vegetative phase and 600 μmol/m²s for 12 hours during the blooming/flowering phase. 

*sdp - short day plant - flowering phase is initiated in short day phase

en-DLI-sample-flowering plants0-12-18h
Time (hours) long / short day phase
ppfd %
Blooming 12h
Vegetation 18h

Yearly distribution of natural Sunlight

The pictures shows the variying DLI through a one year period in a greenhouse. Artificial LED lighting can be used to increase the DLI during times with too less natural sunlight and extend a facilities productive period.


DLI calculator

Provide ppfd value at your canopy level as well as the illumination period.

DLI calculator
Dayli Light Integral

Sun Position

Day and Night Map

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