What Size LED Light for 3×3 Grow Tent? | All Factors to Consider in One Guide

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by Morgan

Last update:

August 29, 2023

How To Choose The Right Lighting For Your Marijuana Grow Room

Indoor growth has many considerations ranging from the size of the grow tent to light output. The first thing you would do is decide on your grow tent's size. This element depends on several factors, with the top considerations being the type and nature of the plants to grow, the number of your plants, and the type of lighting.

What comes next is the light size, which can be challenging if not done precisely. Fortunately, our research into this matter will be of great help. The conclusion here is that what determines the size of the LED light is the light intensity. You also need to consider the coverage area of the LED light, the type of plants grown, and their light requirements.

In this article, we have covered the factors you need to consider when choosing the appropriate LED light size for your 3x3 grow tent. Read through to learn more.

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What Size Led Light for 3x3 Grow Tent - Best Light

As said earlier, the light intensity determines the size of your LED grow light to use in a 3x3 grow tent. Therefore, you'll need an LED light with a wattage of 200W to 300W. The LED light to use should be highly efficient. 

It should also be suitably sized to match the size of the grow tent. This fixture will ensure you get high yields in a compact space.

3x3 grow tent with lights

What Factors Determine the Size of Led Grow Light?

Several factors determine the size of LED grow lights used in indoor growth. We've listed the light requirement, size of the grow tent and type of light. Let's see them in detail.

Light Requirement

Plants have different light requirements. Some plants have high light requirements, while some have low light requirements. 

grow tent

You need to know this aspect as far as the light requirement for indoor growth is concerned.

You'll need a high and efficient light system if you grow flowering plants.

This light is essential in the flowering stage of the plant's lifecycle. Examples of such plants are cannabis plants, tomatoes, orchids, etc.

On the other hand, you need a low light requirement if you have non-flowering plants in your indoor growth system.

Non-flowering plants need low light intensities because they do not produce flowers, which require more light. Such plants may include but are not limited to lettuce and herbs.

Type of Lighting

There are several types of light, ranging from fluorescent to LED lights. All these lights are resourceful in plant growth but with different specifications. However, the best type of light to incorporate in indoor growth is full-spectrum LED grow light

They have several benefits tailored toward providing the best conditions for the growth of plants. For example, they have a range of colors emitting different wavebands of light. Besides, they generate less heat and last longer than other alternatives.

It is with no surprise that many beginners opt for fluorescent lights. They are affordable, reliable, and need no extra fixtures. However, the only limiting factor is that they have low intensity. Therefore, they are inefficient in large-scale growth, limiting you from using them.

You need to be careful when choosing the light type because wrong grow light science may result in plants growing below their full potential.

Size of Growing Area

The size of your grow tent, or the growth area will dictate the size of the LED grow light. If you have a small growing area, you'll need a smaller and few LED grow lights.

However, large growing areas call for larger and many LED grow lights to increase the coverage area, allowing the light to reach all plants evenly.

Measure your growing area first if you're not sure about it. If you have not yet decided on the growing area, first determine the size of the plants you want to grow.

Larger and tall plants need large grow areas, while small and short plants are comfortable in small growing areas.

plants in a grow tent

LED Grow Light Size Vs. Coverage

LED grow lights, like any other light, have a limit on the extent of the light coverage. The extent of how far your LED light will cover depends on its size. For instance, a small 150W LED light only covers 2 x 2 feet, while a large 1000 Watt LED grow light can cover up to 5 x 5 feet.

These figures should guide you in approximating the size and number of LED grow lights you need for your project. For example, say you have a 200sq. Ft growing area and you have the 1000W LED grow lights and 150W LED grow lights. 

For the 1000W light, you'll need eight bulbs (200/25=8), while for the 150W LED grow light, you'll need fifty bulbs (200/4=50). Thus, opting for the 1000W LED grow lights would be a better option than the 150W one.

However, the accuracy of these settings can be wanting. Despite having the same wattage specifications, Grow lights do have different maximum coverage.

LED Grow Light Size Vs. Wattage

The wattage requirement of your LED grow light is another way you can undermine the size and number of the lights you'll need for your grow tent. Plants with high light requirements need higher wattage. For example, a cannabis plant with high light requirements will require 30-70W per square foot.

For our grow tent, which is 3×3, the total square footage will be 9 sq. ft. Given that we need 50W per square foot, the total wattage required will be 450 (9 x 50). Therefore, if you have 1000W grow lights, you'll need only one bulb (450/1000). However, if you opt for 150W LED grow lights, you'll need three bulbs (450/150).

plants growing under the lights

How Many Watts Per Square Foot Do I Need When Using Led Grow Lights?

Using the wattage per square foot to determine the size of LED grow lights is the most efficient and reliable way to do so. However, determining the power draw of a LED grow light may be challenging because there are many variations in lights, and many manufacturers provide inaccurate specifications for marketing purposes.

For example, the 3 × 3 feet grow tent has a total area coverage of 9 sq. ft. Given that we need a 30W per square foot for our LED grow lights, you'll need a total of 270 watts. If you want to use a 150W LED light fixture, you'll need two of them to cover the whole area efficiently.

However, this method does not consider the efficiency of the light as a factor. Therefore, the efficiency of two bulbs with the same wattage may differ in terms of their output power. This feature can cause you to provide too much light or less light to your plants. Wattage shows the light amount a grow light provides, while their output will vary depending on the light brands.

LED Grow Light Size Vs. Output

Determining the actual output of a LED grow light may not be an easy task. However, if the process is a success, it gives the true value, which will accurately determine the size and number of bulbs you need. There are several ways you can use to measure light output. 

However, the simplest way is to use the Photosynthetic Photon Flux Density (PPFD) method. This method lets you determine the amount of light a wavelength of light produces for plants' photosynthesis rather than the amount of light visible to the human eye. The unit of measurement is umol/m²/s.

For efficiency and best results, you need to ensure your plants need around 300 - 600 umol/m²/s and 600 - 1000 umol/m²/s at the vegetative and blooming stages. So the minimum you can subject your plants to is 100 umol/m²/s light output.

marijuana growing in the tent


What Size Led Grow Light for a 3x3 Grow Tent?

A two-inches thick LED grow light is enough for a 3x3 grow tent. It should also have a short hanging height; ideally, it should be 6 - 12 inches. This light should at least produce a photosynthetic photon flux density (PPFD) of 580 μmol/s/m² and 1160 μmol/s/m² in the vegetative and flowering stages, respectively.

How Many Plants Should I Grow in a 3x3 Tent?

You can grow two to four plants in a 3×3 grow tent. However, this number can vary depending on how you train your plants. Also, the size of the plant matters most. Larger plants will only allow you to grow a few of them, while smaller plants give space allowance for more plants within the small grow space.

What Size Led Do I Need for My Grow Tent?

The size of LED grow light you need for your grow tent varies depending on several factors. The most common factors that determine this size are the size of the grow tent, the light requirements of the plant, and the type of plant.

How Many Watts Led 3 Plants?

Growing three plants on your grow tent will need you to supply wattage of between 140W to 240W. This process can happen if you have an average growing space of about six square feet and the wattage per square foot is 32 watts/sq ft, and the average area in square feet per plant is 2.0 sq. ft/plant.

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About the author 


I discovered the benefits of Cannabis at a young age in 2002, with years of trial and error, my knowledge grew just like my plants. As my love for cannabis unfolded I began to teach and learn, trying to gain as much information and practical growing experience.

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