DLI for Autoflowers: Ideal Chart by Growth Stage
Quick answer: DLI (Daily Light Integral) is the total amount of light your plants receive each day. For autoflowers, aim for roughly 12-20 mol/m2/day as seedlings, 20-35 during veg, and 35-45 in flowering. Because autos run on a fixed internal clock, hitting the right DLI at each stage, without overdoing it early, is key to strong growth and good yields.
DLI, or Daily Light Integral, measures how much usable light (PAR) your plants get over a full day, combining both intensity and how long the lights are on. It is one of the most useful numbers in indoor growing because it tells you whether your plants are getting too little, too much, or just the right amount of light.
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Fat Bastard
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THC | 30% - 38% (High) |
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Type | Feminized |
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Yield | High |
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Fat Bastard Auto
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THC | 30% - 38% (High) |
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Type | Autoflowering |
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Yield | High |
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Phenotype | 50% Indica / 50% Sativa |
For autoflowers this matters even more than for photoperiod plants, because autos flower on their own schedule regardless of the light cycle, so you cannot ‘fix’ a slow start later by flipping to 12/12. Getting DLI right at each stage is how you make the most of an auto’s short life. The chart below gives target ranges, and the sections after explain how to measure and hit them.
| Growth stage | Target DLI (mol/m2/day) | Notes |
|---|---|---|
| Seedling | ~12-20 | Go gentle; too much light stresses young autos |
| Vegetative | ~20-35 | Ramp up gradually as the plant builds |
| Flowering | ~35-45 | Peak demand; higher DLI supports bud development |
What Is DLI and Why It Matters for Autos
DLI is expressed in moles of light per square meter per day (mol/m2/day). It is calculated from the light intensity reaching your plants (PPFD) and the number of hours the lights are on, so you can raise DLI either by increasing intensity or by running a longer photoperiod. For autoflowers, many growers use long daily light periods like 18 to 20 hours throughout, which helps reach good DLI at moderate intensity.
Why it matters: too low a DLI and autos grow slowly and yield less; too high, especially early, and young plants get light-stressed and bleached. Because an autoflower’s timeline is fixed and short, there is little room to recover from either mistake, so matching DLI to the plant’s stage is one of the highest-impact things you can control.
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How to Calculate and Measure DLI
The formula is simple: DLI = PPFD x 3600 x hours of light / 1,000,000. In plain terms, measure the PPFD (light intensity) at canopy height, multiply by the seconds of light per day, and convert to moles. If that sounds fiddly, many grow-light apps and online calculators will do it once you enter PPFD and photoperiod.
To measure PPFD you can use a dedicated PAR meter, a quantum sensor, or a smartphone app with a correction factor (less precise but useful). Take readings at several points across the canopy, since light falls off toward the edges. For the intensity side of the equation, see our guides on PPFD for seedlings and the best PPFD for seedlings.
Dialing In DLI at Each Stage
Start low. Seedlings and young autos only need a modest DLI of roughly 12-20; pushing bright light too early is a common cause of stunted, stressed starts. As the plant moves into vegetative growth, raise the DLI into the 20-35 range gradually, letting it build a strong frame of leaves and stems.
Flowering is when autos want the most light, generally around 35-45, to fuel bud development, which is what growers mean by the ‘cannabis DLI for flower’. Going much above the mid-40s rarely helps and can cause light burn or bleaching, especially without enough CO2 and airflow. Watch the plants: tight, pale new growth or bleached tops means too much, while stretchy, thin growth suggests too little. For how long to run lights, see our guide on grow light hours.
Signs Your DLI Is Too High or Too Low
Your plants will tell you whether the DLI is right. Too much light shows up as bleached or yellowing tops nearest the lamp, tight and crinkled new growth, and sometimes upward-cupping or ‘tacoing’ leaves; the plant is getting more light than it can process. The fix is to raise the light, lower its intensity, or shorten the photoperiod until the stress signs ease.
Too little light looks different: stretchy, leggy growth with long gaps between nodes, thin stems, and pale, lanky plants reaching for the lamp, along with disappointing yields. Here you want to lower the light closer to the canopy or increase intensity. Because autoflowers run on a fixed timeline, check them often and adjust early, correcting DLI in week one is far more effective than trying to rescue a stressed plant later in its short life.
Frequently Asked Questions About DLI for Autoflowers
What is the ideal DLI for autoflowers?
Aim for roughly 12-20 mol/m2/day for seedlings, 20-35 during the vegetative stage, and 35-45 in flowering. Autoflowers are sensitive to too much light early on, so start low and increase gradually. Going much above the mid-40s in flower rarely helps and can cause light burn or bleaching.
What DLI do autoflowers need in flower?
During flowering, autoflowers generally want a DLI of about 35-45 mol/m2/day to support bud development, their highest demand of the whole cycle. Provide enough airflow and, ideally, CO2 to use that light well. Pushing much higher risks light burn and bleached tops without improving yield, so stay in range.
How do you calculate DLI?
Use DLI = PPFD x 3600 x hours of light divided by 1,000,000. Measure PPFD (light intensity) at canopy height with a PAR meter or app, multiply by the seconds of light per day, and convert to moles per square meter. Many grow-light calculators do this automatically once you enter PPFD and photoperiod.
What happens if autoflowers get too much light?
Too high a DLI light-stresses autoflowers, causing bleached or yellow tops near the lamp, tight crinkled growth and cupping leaves, without improving yield. Because autos cannot recover lost time, it is better to stay within the recommended ranges (around 35-45 in flower) and raise the light or lower intensity as soon as you see stress.
