Enter the total PPFD and the light hours per day into the calculator to determine the daily light integral (DLI).

DLI Formula

The following formula is used to calculate a DLI.

DLI = PPFD* LFD * (3600/1,000,000)

• Where DLI is the daily light integral (mol/m^2/d)
• PPFD is the photosynthetic photon flux density (umol/s*m^2)
• LFD is the light hours per day

DLI Definition

DLI stands for daily light integral and it is a measure of the total number of photosynthetically active photons (those in the range of 400-700nm) that are delivered to an area over a given period.

Example Problem

How to calculate DLI?

1. First, determine the total number of light hours per day.

For this example, the total number of light hours the area receives per day is 10 hours.

2. Next, determine the PPFD.

In this case, the photosynthetic photon flux density is found to be 15 umol/s*m^2.

3. Finally, calculate the DLI.

Using the formula above, the daily light integral is found to be:
DLI = PPFDl * LFD * (3600/1,000,000)
DLI = 10 * 15 * (3600/1000000)
DLI = .54 mol/m^2/day