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Detailed Guide To Choosing The Right Size Grow Tent For Your Plants

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.

You can figure out how many plants fit in your grow tent by carefully estimating the amount of space your plants will consume compared to the amount of space available in your grow tent. You’ll also need to measure for other items you plan to keep in the grow tent.

Luckily, I did all the work for you, and I measured for several different size tents.

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
  • 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.

The short and sweet:

I’ll save you a bunch of reading and provide some immediate answers regarding what size grow tent you’ll need for each number of cannabis plants.

But I encourage you to read through the detailed explanation below to understand the reasoning behind the grow tent sizes I’m recommending.

All of these recommendations are assuming you’ll be planting with 3 or 5 gallon grow bags/buckets.

What size grow tent for 1 plant:

I recommend a 24″x24″x48″ grow tent for one cannabis plant.

What size grow tent for 4 plants:

I recommend a 48″ x 48″ x 80″ in. grow tent for four plants.

What size grow tent for 6 plants:

I recommend a 60″x60″x80 in. grow tent for six plants.

What size grow tent for 8 plants:

I recommend one 96″x48″x80″ in. grow tent

OR

*Two* 48″ x 48″ x 80″ in. grow tents

What size grow tent for 10 plants:

I recommend a 96″x48″x80″ in. grow tent for ten plants.

What size grow tent for 12 plants:

I recommend *two* 60″x60″x80 in. grow tents for twelve plants.

What size grow tent for 14 plants:

I recommend one 96″x48″x80″ in. grow tent + One 48″ x 48″ x 80″ in. grow tent.

What size grow tent for 16 plants:

Using 3 or 5 gallon grow bags: *Two* 96″x48″x80″ in. grow tents

What size grow tent for autoflowers:

Autoflowers typically grow 2ft tall at most. I’d follow the same guidelines laid out above if you’re considering growing autoflowers in a grow tent.

If you’re wondering how many autoflowers you can fit in a 4×4 grow tent compared to regular size cannabis plants, you can maybe fit one extra.

Even though autoflowers are smaller, they can still take up considerable width when they’re fully matured, even if their height is shorter.

Therefore I wouldn’t expect much space savings from growing autoflowers compared to regular cannabis plants in a grow tent.

However, if you’re only growing one or two autoflowers, you may be able to get away with a 4’x2′ grow tent which features a lower ceiling compared to the 4×4.

Remember: These are rough estimates based on ~20 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)
1 gal. 16cm 18cm
2 gal. 20cm 22.5cm
3 gal. 23cm 27cm
5 gal. 27.5cm 31.5cm
7 gal. 29cm 36.5cm
10 gal. 31cm 40.5cm
15 gal. 33cm 46cm
20 gal. 40cm 51cm

 

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.

5gal plant

Mature plant in a 5 gal. grow bag

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.

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!

best led grow lights

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’s one simple trick to control your cannabis plant’s height. 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.

In other words, initiate your plant’s flowering phase when it reaches half the desired ultimate height.

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.

If you’re still in the vegetative growth phase and your plant is already too tall, you can prune the plant down to half your desired ultimate height. It’s safe for your plant and it’ll survive the pruning.

Other less definitive methods for controlling plant size in a grow tent are reducing light intensity, moving tallest plants to the edge of the light coverage area, and reducing the flowering light cycle from 12/12 to 11/13 or 10/14 to really forbid any new branches or leaves from growing.

That’s it!

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!

FAQ:

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.

 

 

References:

1. Chandra, Suman, Hemant Lata, Ikhlas Khan, and Mahmoud Elsohly. “Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions.” Physiology and Molecular Biology of Plants 14.4 (2009): 299-306.

2. Backer Rachel, Schwinghamer Timothy, Rosenbaum Phillip, McCarty Vincent, Eichhorn Bilodeau Samuel, Lyu Dongmei, Ahmed Md Bulbul, Robinson George, Lefsrud Mark, Wilkins Olivia, Smith Donald L. (2019). “Plant Growth-Promoting Rhizobacteria for Cannabis Production: Yield, Cannabinoid Profile and Disease Resistance.” Frontiers in Plant Science 10. 10.3389/fpls.2019.00495

Other References:

GrowWeedEasy

Nick
 

My name is Nick, and I'm a home grower who spends time writing about indoor growing tools and setups. My goal is for 420ExpertGuide to be a one stop shop for indoor growers to find the information they need.

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