Cannabis Lighting Calculator

Recommended DLI and PPFD values for Cannabis per week and stage

The light requirements for cannabis are extremely well studied. The optimal amount of light changes throughout the grow cycle and depends on the flowering type. Learn more in our deep dive on cannabis lighting requirements.

Inputs

Flowering type

Grow Stage

Germination Vegetative Flowering

Adding CO₂

Photoperiod

Recommendation

DLI – mol/m²/d

PPFD – µmol/m²/s

Recommended cannabis DLI by grow week

Recommended DLI (mol/m²/d) for cannabis at each week of a typical 15-week grow cycle, with and without CO₂ supplementation. Peak vegetative light intensity hits at weeks 5–6 (40–45 DLI, or 50–55 with CO₂). Flowering ramps from ~30 to 40 DLI between weeks 9 and 13, then tapers as the plant matures. Source: Photone's cannabis grow-cycle reference.

Week	Grow Stage	DLI (mol/m²/d)	DLI + CO₂
1	Germination	12	12
2	Germination	16	16
3	Vegetative	20	25
4	Vegetative	30	38
5	Vegetative	40	50
6	Vegetative	45	55
7	Vegetative	25	31
8	Vegetative	28	35
9	Flowering	30	38
10	Flowering	34	42
11	Flowering	36	45
12	Flowering	38	48
13	Flowering	40	50
14	Flowering	36	45
15+	Flowering	32	40
Values shown are for regular (photoperiod) strains; autoflower recommendations diverge from week 7 onward — use the calculator above for autoflower values.

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Inputs

Recommendation

Recommended cannabis DLI by grow week

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