Are you wondering what size grow tent you’ll need for the number of cannabis plants you plan to grow? I’ve broken down all the factors to be considered to make the decision process take no longer than a few minutes.
Generally speaking, you should have 2×2 feet of grow space per adult cannabis plant in your grow tent. You also need to have space for other items like a humidifier.
These estimates are assuming you do not train your plants. Training cannabis plants involves bending the plant stems to provide more light exposure to more bud sites. Depending what training method you use, that might end up taking up additional space per plant. I’ve seen single cannabis plants trained to take up an entire 3×3 foot grow tent.
After following this guide you’ll have answers to the following questions:
- What size grow tent for 4 plants? What size grow tent for 8 plants? What size grow tent for 12 plants? And so on…
- What size grow tent for autoflowers?
- How tall should the grow tent be?
- How to control your plant’s height inside a grow tent
- Other factors to consider when shopping for grow tents
Ultimately it comes down to how well you can utilize a given space, and taking steps to ensure you’re getting the most out of that space.
How many cannabis plants per grow tent?
All of these recommendations are assuming you’ll be planting with 3 or 5 gallon grow bags/buckets.
What size grow tent for 1 cannabis plant:
I recommend a 24″x24″x48″ grow tent for one cannabis plant.
What size grow tent for 2 cannabis plants:
I recommend a 24″x48″ grow tent for two cannabis plants
What size grow tent for 4 cannabis plants:
I recommend a 48″ x 48″ x 80″ in. grow tent for four plants.
What size grow tent for 6 to 8 cannabis plants:
I recommend one 96″x48″x80″ in. grow tent
What size grow tent for 10 cannabis plants:
I recommend one 96″x48″x80″ in. grow tent plus one 24″x48″ in. grow tent for ten plants.
What size grow tent for 12 to 16 cannabis plants:
I recommend *two* 48″x96″x80 in. grow tents for 12 to 16 cannabis plants.
What size grow tent for autoflowers:
Autoflowers typically grow 3ft tall. I’d follow the same guidelines laid out above if you’re considering growing autoflowers in a grow tent, and here’s why:
Even though autoflowers are smaller, the branches can still take up considerable width when they’re fully matured, even if their height is shorter.
Therefore you shouldn’t expect much space savings from growing autoflowers compared to regular cannabis plants in a grow tent. You might be able to squeeze one extra in there. But it’s not a drastic difference in the amount of space you’ll have.
Remember: These are rough estimates based on ~24 square inches of space needed PER PLANT using a 3 or 5 gallon grow bag. Below I’ll describe methods for maintaining your plant’s height and size so you can actually fit this amount of plants in your grow tent.
Determine the space needed per plant:
Cannabis plants can grow in a range of sizes, many of which are controllable. Determining how much space you’ll need per plant is a great start to determining how much total space you’ll need in a grow tent.
The most commonly used grow bags for home-growing cannabis are three and five gallon grow bags. A good rule of thumb is to allow 2 gallons of soil for each foot of desired plant height.
For determining the total space needed inside your future grow tent, I’ll start by breaking down the diameters of different size grow bags.
|Grow Bag Size (Gal.)||Height(cm)||Diameter(cm)|
Take a look at the diameters above for each grow bag size. But you can’t stop there , because the plant’s branches will ultimately grow beyond the edge of the grow bag.
For 3 and 5 gallon grow bags you should consider the cannabis plants can grow 13-15cm beyond the edge of the grow bag on any given side.
So in total if you’re looking to grow four plants in 3-gallon grow bags, you should set aside 44-49cm (16-17.5in) of space per plant.
That’s 27-32cm for the grow bag, plus 16-17cm of space beyond the edge of the grow bag, for a total of 44-49cm per plant using 3 or 5 gallon grow bags.
If you plan to grow in larger bags/buckets, you should expect the branches will potentially grow further than the 13-15cm estimated for 3 or 5 gallon grow bags, so leave even more breathing room for your cannabis plants.
So what size grow tent do you need for 4 marijuana plants? Technically you could tightly squeeze them into a 3x3ft grow tent, but you wouldn’t have space for a standing fan or humidifier. You could still hang stuff from the top of course.
If you want a comfortable fit for 4 cannabis plants in 3-5 gallon grow bags (plus a humidifier), ideally you should go with a 4×4 grow tent (48″x48″x60″ in.)
How tall should my grow tent be?
If you’re growing cannabis or a tall vegetable plant like tomatoes, you should definitely stick with the standard 80-inch height on the 4×4 grow tents. This is why:
Your grow light will hang about one foot from the ceiling of the grow tent, and depending on the strength of your grow light you’ll need 18-24 inches between the grow light and the plant surface.
So right off the bat you’ve used up 2.5-3ft of height. That leaves you with 3.5ft for your cannabis plants, maybe a little more if you’re able to string your grow light up a little higher. Of course, you can always use a dimmer on your grow light, but the light won’t penetrate to the lower branches of the plant.
If you’re growing smaller plants like succulents or house flowers, you may be able to get away with a mini grow tent that has a smaller height.
Leave space for a humidifier in your grow tent:
One benefit of growing plants indoors is the ability to control the environment to obtain the best harvest possible.
When you’re asking yourself what size grow tent to purchase, please remember to get one with enough room for your plants PLUS a humidifier!
I really like this 6 liter humidifier. The digital display that lets you set the exact humidity level on your own so humidity levels don’t turn into a guessing game. It also has a large tank that doesn’t require refilling every few hours.
It’ll take up about 11 inches by 7 inches of space in your grow tent. I worked out the measurements, and you can squeeze one of these humidifiers into a 4×4 grow tent with 4 cannabis plants.
Side note on grow tent humidity:
Humidity is a big factor when growing cannabis. Air that’s too dry will stunt growth, and too humid can cause mold or rot.
Cannabis clones need 70% humidity because they mainly absorb water through leaves while their roots are forming.
50% humidity is sufficient to get you through the remainder of the vegetative and flowering growth cycles.
If you’re growing tomato plants they’ll need 70-80% humidity since tomatoes are mostly water.
Succulents will require a much more dry environment with only 10-30% humidity.
Controlling Plant Height In Your Grow Tent:
If you truly want to be able to fit 4 plants in a 4×4 grow tent, controlling your cannabis plant height will be crucial.
Luckily, there are a few tricks to control your cannabis plant’s height.
Switch plants to flowering phase at the right time:
During the vegetative growth phase, when your cannabis plant has reached half the height you ultimately want it to reach, change your lighting cycle from 18 hours to 12 hours.
The reasoning is your plant will still grow the other 50% during flowering cycle. This has proven to be a good rule of thumb and will help you grow the right sized plants for your grow tent’s size.
Top Your Cannabis Plant:
Cut off the top node upward from your plant’s main stem. Not only will this limit the height of the plant, it will diffuse hormones downward to the larger branches and help them produce more bud.
Low Stress Train Your Cannabis Plant (LST):
Early in the vegetative phase, you’ll want to bend your largest branches over to the side of the grow bucket and tie them down somehow. The branches will naturally turn upwards again toward the light, but this method will decrease the ultimate height of your plants. Read more about LST in my post about maximizing cannabis yields.
Use a smaller grow bag to grow smaller plants
If you’re worried about your cannabis plants taking up too much space inside your grow tent, you can help restrict their ultimate size by giving the roots a smaller area to grow in. Use a 3 gallon grow bag instead of a 5 gallon grow bag. Likewise if you want one larger sized plant to take up your entire grow tent, you can consider a 7 or 10 gallon grow bag to allow for a larger root system.
Do More Cannabis Plants In One Grow Tent Equal More Yields?
Squeezing as many plants as possible into one space won’t necessarily equal more yields. Crowding your tent means your plants will figuratively be fighting each other for light and CO2. Proper plant spacing was one factor mentioned in a McGill University study about cannabis yields.
Don’t get me wrong, 4 plants in a 4×4 foot grow tent will yield you more than two or three plants in a 4×4 foot grow tent. I’m talking about trying to overcrowd 5 or 6 adult size plants into a 4×4 foot grow tent.
Light will also be a big factor. If your lighting isn’t strong enough, you could end up with the same harvest from 1 to 2 plants as you would from 3 or 4 plants. Read my guide on proper light strength and coverage here. You can also read my guide for maximizing yields here.
You’re now fully prepared to purchase the right size grow tent that’ll fit any number of plants you desire. These are general guidelines that should work out just fine.
However, you should remember that more space is better if you have the flexible budget to go one size up and provide your plants a little more breathing room. But in the end it’s totally up to you.
If you’re buying a grow tent soon, don’t forget to check out my guide to choosing the proper sized grow tent fan, and my guide to the top grow tents on the market! Also learn how to lower temperatures in your grow tent.
How much grow tent space per plant?
You can control how much space each plant takes up in your grow tent. Using 3 or 5 gallon grow bags, I estimate you’ll need 44-49cm per cannabis plant.
How many cannabis plants fit in a 4×4 grow tent?
You should be able to grow 4 cannabis plants using 3 or 5 gallon grow bags, plus have room for a humidifier.
How do I control cannabis plant height?
When the cannabis plant reaches half of your desired height, initiate flowering by reducing light exposure from 18 to 12 hours daily.
Do I need a humidifier for my grow tent?
Humidity is a crucial part to growing cannabis and preventing powdery mildew which can destroy your plants. Leave extra space (about 12×6 inches) for a humidifier.