cannabis lumens per square foot

cannabis lumens per square foot

1000 to 1200 watts)

120 to 140 watts)

Assume about 32 watts/sq ft (actual LED wattage) for flowering. Fewer watts might equate to smaller yields while more wattage may lead to larger yields.
240 to 300 watts)

Different LED grow lights will have different efficiencies. More efficient LED grow lights will use fewer watts to emit the same amount of light that a less efficient LED grow light will exude. Therefore, as mentioned above, wattage is not the most accurate tool to know how powerful of a grow light you need for a particular coverage area.
250 to 300 watts)

500 to 650 watts)

When we talk about wattage inthis article, we are referring to the wattage drawn at the wall, not what the manufacturer states as “LED wattage” – which is typically the product of the maximum LED wattage and the number of LEDs. For example, 300 x 3-watt diodes would be a 900 watt LED grow light. However, the LED grow light might only draw 500 watts at the wall.
900 to 1100 watts)

The Ultimate Guide to Help You Choose the Correct Wattage for Your Grow. If you are wondering how many watts of LED power you need for your grow, then read on.
I need to know the recommended lumens per square foot.
the lumen number on a light bulb package refers to its output at a reference point either at the point source or the surface of the bulb
if money is no object they make a new light meter that measures
plant usable light they are called quantum meters they read in a new unit called micro einsteins they start around 200$
for hid lights assume low for about half the lumen number at 18 inches away [ you still might have heat issues at that distance]
i did the light meter and tape measure stuff a while ago so this is based on real measurements although i am not a tech geek grower
to make it simple for CFLs at 3=6 inches away you get about 2/3 – 3/4 the lumen number on the package
there are tables on the web that give conversion for common light sources to micro einsteins
lumens lux and footcandles all measure the intensity of a light source
this output decreases with distance some inverse square ratio
to get a real usable light intensity i use an old fashoned light meter for photography in the incident mode [this is the little
white dome thing — it measures the light actually falling on the point of measurement]
I need to know the recommended lumens per square foot. I read this somewhere on the site but can’t seem to find it now. If someone could help me out on…

1000 to 1200 watts) 120 to 140 watts) Assume about 32 watts/sq ft (actual LED wattage) for flowering. Fewer watts might equate to smaller yields while

Lumens. and How much your Grow Room needs!!


so i hear that veg stage needs roughly 2,5k to 3k per sq ft.

then I heard flowering stage they need 10k per square foot.

doesnt the sun give out like 8k per sq at max?

and cant the plant only absorb 7.5k per sq foot?

my setup is 4×5 putting it at 20 sq ft.

I plan on using yieldmaster [SunSystem] 600w Hortilux at about 95k lumens.

will i have any problems in flowering stage?

some skeptics have made me skeptical.

any friendly experts out there?

thanks in advance,

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That is not what books on the subject say. They list 7.5 as the upper limit of plant utilization (marijuana growers bible).

Its easier to deal with watts/foot or some other measure as there allot of factors that go into the footprint of your bulb. Chiefly, your hood design. All hood are not created equal. Therefore, people often state a size of a grow area instead of lumens. I wish people would stop talking in lumens and just talk lux because lux is the only thing you can measure, and when you get down to it,is the more important of the two. Your 9.5k bulb will fade to about 7.5k in about 6-8 inches.

Yeah, your bulb gives off X amount of lumens.. how many of those lumens are actually reaching your plant though? That’s the really important part. Lux is the common measure of light intensity that you can actually measure. 1k lux equals ROUGHLY 10k lumen. I probably spent 3 hours with my lux meter and a grid finding the best height for my hoods and the size of my SCROG net.

When dealing with these issues it is best to consult the published books on marijuana cultivation and setting up grow rooms. If you pick through forum responses you will inevitably find a piece of information that is not really correct, or partially correct..thus making your decision making process more difficult.

Based on my literature review..

Optimum grow space per bulb
400 watt system 3×3
600 watt 3.5 x 3.5
1000 watt 4 x 4

Most efficient duration for veg growth = 18 hours a day. After this point, the ability of the plant to process light and produce sugars fades rapidly. 18 hours is the point of diminishing returns. You can piss away your money on electricity but those extra 6 hours are getting you less and less return as you go past 18.

Most efficient Co2 = 1300 PPM. The rate of photosynthetic rate increase with increased co2 saturation is not linear. It increases rapidly at first, levels off, then increases again with temperature. The rate of increase pretty much flat lines at 1300. From 1300 to 1500 there is a TINY increase but to me (because I have an advanced ppm controller) that extra 200 is kind of wasted.

just my 2 cents. Some people want to provide the ultimate growing environment and some people are growing plants in a computer case with a single CFL bulb. It’s all good in my book.


thanks for response. pretty helpful.

my room is 6.5ft by 3 ft.

im ordering the 600w HPS Hortilux bulb with yield master reflector with mylar on the walls.

(6) 3 gallon pots. 2 rows of 3.

giving each plant about 22″x18″ to grow.

it wouldnt hurt getting a 1000w bulb but 600w would work just fine im sure.

3 gallon pots of indica can achieve like..3-3 1/2, 4 ft if im lucky?

im fine with that. my room is 7 feet tall so with the reflector, and pots, and distance from light i could grow about 50″ max

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you should really look at the supersun 6 hood.. Scored much better in terms of overall light intensity and eveness among 6-7 hoods that were tested.

a 600 watter is not going to effectively penetrate more than 3 or so feet anyways so you are good. I would probably increase planter size, stagger them in rows, and SCROG for the highest yield.

check out the SCROG screen in my grow journal.


ya ive heard many good things of scrog even like 3/4 pd a plant easily.

i was thinking of doing it but this being my first indoor grow i wanna do all natural to really learn the basic steps to indoor growing.

maybe ill top and lst?

or is SCROGing really an easy way to do it?

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Well-Known Member

Unlike some on the forum, I generally don’t post about things that I am not knowledgeable about. Despite the fact that you have 8,700 posts, it seems that you are actually the one that is a little confused on lighting terminology and plant physiology. Your original post (100,000 lumens put out by the sun) is incorrect as is the post that I quoted above. I have seen this number thrown out before by other high posting members but that doesn’t mean its correct. The book I referenced is correct as I have seen those numbers stated other places as well (including this forum). The thread starter post is actually consistent with a number of different discussions that I have read on the subject.

Lux IS directly related to lumens but unfortunately, lumens do not deal with area (which is why its not the best way of figuring out lighting in MJ cultivation). Lux is a measure of luminous flux, but more importantly, lux deals with coverage. 1 LUX is equal to 1 one lumen PER SQUARE METER. That is, how much light energy is actually received by a pre-defined area. How much light is given off really doesn’t matter. If you had a 1,000watt MH bulb (80,000 lumens) 15 feet above your plants. its not going to be enough to support optimal growth.

The sun actually puts out 3.75×10^28 lumens. (that’s 28 zeros after 3.75). Sunlight on the surface of the earth however is around 10k lumens. If the sunlight we see was 100,000 lumens you wouldn’t be able to open your eyes lest you go blind. Don’t believe me, stare into a 1,000 MH bulb and report back.
If you want to get really technical, comparing HID lumens and sunlight lumens in terms of plant utilization is actually flawed as the light sources are very different. The scientific literature says that a plants ability in natural conditions to utilize sunlight peaks at around 5k. For HID lights, it peaks around 7.5k. For HID utilization of this rate you need proper CO2, humidity and temperature conditions. The ability to use more sunlight is really limited by the physical and biochemical processes related to photosynthesis (concentration gradients, evaporation rates, cellular process).

I’m not going to start a thread to ask advice as the topic has been covered quite a bit. like here.

Not trying to be a dick about it either, just trying to ensure that the correct information is presented. If you have information that demonstrates that plants can utilize “way more than 7.k lumens” I would love to see it.

so i hear that veg stage needs roughly 2,5k to 3k per sq ft. then I heard flowering stage they need 10k per square foot… doesnt the sun give out like 8k…