PPFD to DLI calculator

Turn your grow light’s PPFD into the daily light your plant receives. Enter the PPFD at leaf level and the hours the light is on.

PPFD at the plant (µmol/m²/s)From the light’s PPFD chart at your hanging distance.

Where do I find this number?

Most grow lights come with a PPFD chart (sometimes called a PAR map). Look on the box, in the manual, or in the photos of the online listing. It shows how strong the light is at different heights below the lamp.

Find the chart for the height your light hangs above the leaves (for example 12, 18 or 24 inches).
Use the number in the middle, right under the lamp. In this example, 320.
No chart in the box? Search the light’s brand and model name plus “PPFD”.

Only see watts? Watts measure electricity, not plant light, so they can’t be used here. Measure the light with your phone instead.

Hours of light per dayMost indoor plants: 12–14. Maximum 16.

Daily light integral

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mol/m²/day (DLI)

The formula

DLI = PPFD × hours × 0.0036

PPFD measures light arriving each second. Multiplying by 3,600 seconds per hour and by the hours of light, then dividing by 1,000,000 (micromoles to moles), gives the daily total. That simplifies to × 0.0036.

PPFD to DLI chart

PPFD (µmol/m²/s)	DLI at 12 h	DLI at 14 h	DLI at 16 h
50	2.2	2.5	2.9
100	4.3	5.0	5.8
150	6.5	7.6	8.6
200	8.6	10.1	11.5
250	10.8	12.6	14.4
300	13.0	15.1	17.3
400	17.3	20.2	23.0
500	21.6	25.2	28.8
600	25.9	30.2	34.6

Compare the result with your plant’s needs on the DLI chart by plant: about 3–6 for low-light houseplants, 12–17 for herbs, 18 or more for tomatoes.

Open the full DLI calculator to compare with your plant and print it

The formula

PPFD to DLI chart

Sources