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

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## 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?

**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.

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

**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