Grow tools
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Jeff Zorn is the founder of Cannabis Training University (CTU), an online cannabis school with 50,000+ students since 2009. CTU is an IACET Accredited Provider, and its courses cover cannabis cultivation, business, medical cannabis, budtending, cooking, extraction and industry regulations.
How do I work out DLI?
DLI = PPFD × hours of light × 0.0036.
Daily light integral (DLI) is the total light a plant gets in a day, in moles of photons per square meter. 600 PPFD for 18 hours is 38.9 mol/m²/day; the same light for 12 hours is 25.9.
Checked October 2026 · Sources below
PPFD guide: 600–900 typical for home grows; 900+ needs strong climate control (and CO2 above ~1,000).
DLI in mol/m²/day for common PPFD levels and light schedules.
| PPFD | 12/12 (flower) | 18/6 | 20/4 |
|---|---|---|---|
| 200 | 8.6 | 13.0 | 14.4 |
| 300 | 13.0 | 19.4 | 21.6 |
| 400 | 17.3 | 25.9 | 28.8 |
| 500 | 21.6 | 32.4 | 36.0 |
| 600 | 25.9 | 38.9 | 43.2 |
| 700 | 30.2 | 45.4 | 50.4 |
| 800 | 34.6 | 51.8 | 57.6 |
| 900 | 38.9 | 58.3 | 64.8 |
| 1000 | 43.2 | 64.8 | 72.0 |
| 1200 | 51.8 | 77.8 | 86.4 |
Sources: DLI formula — Faust, J.E. and Logan, J. (2018), "Daily Light Integral: A Research Review and High-resolution Maps of the United States", HortScience 53(9): 1250–1257. Light-level study — Rodriguez-Morrison, V., Llewellyn, D. and Zheng, Y. (2021), "Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment", Frontiers in Plant Science 12:646020 (doi.org/10.3389/fpls.2021.646020). Checked October 2026.
Light your grow properly
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