What is this?
This web app has been designed to help you determine daily light integral (DLI) values throughout the year for any location on Earth. It uses worldwide weather station data and algorithms to deliver the most accurate DLI values for your location.
What is DLI?
The Daily Light Integral (DLI) is a measure of how much daylight is delivered to a location over a 24-hour period. More specifically, it is defined as: “photosynthetic photon flux density (PPFD) integrated over a 24-hour period, typically coinciding with the 24 hours of a calendar day”. It is expressed as moles of light per square meter per day (mol * m-2 * d-1).
Why is it important?
Plant growth is driven by light. The ability to calculate DLI values for any location opens up many possibilities. Growers can estimate how much supplemental lighting will be needed throughout the year to allow a plant to reach its potential growth in a greenhouse, and they can also calculate the amount of shading needed for their crops. Outside the greenhouse, growers can determine whether crops grown in an open field will receive sufficient light during the course of a growing season to reach maturity.
Fig. 1 – DLI Calculator
 Faust, J. E., and J. Logan. 2018. “Daily Light Integral: A Research Review and High-resolution Maps of the United States,” HortScience 53(9):1250-1257.
 It is important to remember that the amount of light incident upon the plant canopy in a greenhouse may be between roughly 40 and 60 percent of the amount of light incident on an open field adjacent to the greenhouse. The actual values depend on the glazing transmittance, the greenhouse roof design, the building orientation, whether the glazing is transparent or translucent, the amount of cloud cover, and more. SunTracker Technologies’ Cerise365 + Greenhouse Designer can calculate accurate DLI values inside greenhouses, hybrid vertical farms, and building atria.