Start using DLI

Well, I posted these in another thread, but seems like they’d be a good fit here.

DLI is just a measure of light over time. PPFD is a snapshot of light right now. DLI is how much light your plants get in a day with the given ppfd. If you have a ppfd measurement and know how many hours a day your lights are on (I hope we all do) you can just plug it into a DLI calculator online. Literally just search DLI calculator.

While optimal lighting will vary based on a lot of factors, the graphs above are a good starting point. The bottom number is the one most of us will use. Give them a try and adjust up or down a little til you find the sweet spot for your grow. Experience is probably the best thing to go off, but for those of us who lack it a reference is good.

My phones are all cheap and won’t run the app, but my kid’s overpriced tablet and the Photone app have been a game changer for me.


@Stoneman this is an important chunk of knowledge. Nicky’s original post has so much value.

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Good evening, I had another question that occurred to me yesterday. People give recommendations on wattage per square foot or if you have X x X tent you need X wattage light. I’ve found by using DLI these recommendations are way high now. I have an HLG 550v2 which I am absolutely loving. That said using DLI I will get nowhere near using the full potential. I’m using a 4x4 and at 45dli the max I’ll get according to the auto chart I’m using 275 watts I tested earlier. That’s the max I’ll get and later in flower I’ll actually be using less. So is this conflicting info? Have times changed and now someone with a 4x4 could theoretically get by with a 250 watt light? Just confusing is all and I was really hoping to blast my plants with some more wattage.

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The recommendations are usually based on coverage area of the light at a particular height, and for both veg and flower, and don’t take any reflectivity of your grow space into account. But when we bring DLI into the equation the height becomes a variable vice a constant. Add to that the difference between 18 and 12 hours of light, and you will find that you need more power to maintain that DLI when you are only running the lights 2/3rds of the time.


Got ya. That makes sense since I was only thinking in terms of Autos. I run 20/4 so don’t need much power at all to get my DLI. I had totally forgot about photos or usimg other time schedules. Thank you for that I knewt ( see what I did there) you would help explain it :slight_smile:

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Awesome info brother! :beers:
I run my tents at the upper co2 levels of light and no co2 and no issues whatsoever. As long as I keep my canopy temps below 85°, and humidity in check. Things run smooth.
Just chopped these girls yesterday and they don’t look like they’ve suffered any ppfd and high dli problems. :man_shrugging:


Look primo IMHO.


Hey outlaw.

We are starting to see more and more people speak about DLI, it’s great, as for light values there will always be difference of opinions out there.
In my original post I explain the different effects more light has and some theory as well.
The cannabis guru Bruce himself said clones can handle 60DLI

So the first chart you posted I personally wouldn’t agree with but the second sounds more fitting. Autoflow vs photo period, there is no proof that autoflower use more or less light currently.


I thought the photoperiod chart was quite odd too. It makes it look like you shouldn’t turn your light intensity up when you go to 12/12. That’s where that experience comes in handy. Thanks.

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Well after reading your thread in it’s entirety early on. I went with exactly what you stated brother @Nicky . My plants get hammered with light rather quickly and pull back like you said about seeing foxtailing towards the end. The 2 plants I posted about 3 or 4 posts up are the result of your info my friend! Appreciate what you do for the community :pray: :beers:


Those turned out really nice, but that’s just my opinion :smile_cat:.

What strain? Purple kush?
By who?

You did a really good job of lollipoping and defoilating, a textbook result imo
Congrats @The_Chef


Yeah, dialing lights up pre stretch is key to help control the stretch as much as possible and avoid a leggy plant. Many times genetics will play such a role we can’t control it fully but lower light levels then just seems to the opposite as to what I would do and what our Dr of cannabis research Mr Bugbee has led us to understand

:rofl: I literally screen shot your post. Really appreciate the kind words brother. One hell of a confidence booster for sure!

The strain is Dark Devil from Sweet Seeds genetics. It is a Purple Kush auto cross with Big Devil XL auto. :call_me_hand: