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How Many Watts Per Square Foot for Led Grow Lights You Need?

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This is a frequently asked question. However, there is no exact answer to it. The watts needed per square foot for LED grow light depends on various key factors.

In this article, we will share with you the factors that should influence your choice for watt level of the grow light you choose. And most important we will help you with calculations for the wattage level you need under every circumstance. You will also get recommendations for the best-LED lights to buy today.

Let’s get started.

Factors to Consider When Choosing LED Light Watts Per Square Meter

How Many Watts Per Square Foot for Led Grow Lights You Need

To be able to know the watts per square foot for the LED Grow lights, you need to consider the following factors.

1. Your Crops

The first thing that will determine the light needs for your grow light is the nature of your grow. You must consider your crops above anything else.

Some LED lights are designed for a particular grow. In the market, you will find different LED lights with different Watt power designed for growing different plants. In general, you will find LED lights for growing flowers, herbs, medical plants, vegetables, and small plants (but not limited to only these plants).

Under your crop, you also need to consider the following specific factors.

  1. Type of plant

Some plants will require more light while others need average light. For instance, plants with canopy need more light to penetrate through them. This means you will be needed to buy lights with more watts.

So, before you can decide on the wattage for your square meter, you need to know which plants are in your grow tent.

Herbs require average lighting. Other plants such as pepper, cannabis, and tomatoes require a high light intensity.

  1. Grow Stage

Plants undergo different phases from germination, vegetative, and flowering. In each phase, plants will need a different level of light intensity.

During germination, plants don’t require light, as they germinate they require less light. The need for light increases at the vegetative phase. At flowering, you will also need a high light requirement for your plants to produce large buds.

However, during flowering, you need to reduce the number of hours you expose your plant to high-density light. There should be more hours of darkness than light.

  • Number of Plants in a Grow Tent

Plants need breathing space. As much as you need to get the maximum yield from your Grow Tent, you need to plant the right number of plants.

The higher the number of the plants in a grow tent, the higher the light intensity you need.

2. Size of Your Grow Tent

The size of your grow space is another critical factor to consider when choosing the watts of a LED unit. Different grow tent size will accommodate a different number of plants hence the need for a different level of Wattage.

A large, grow tent will require a high LED light intensity.

Below is the standard Wattage level for different grow spaces. These wattage does not consider other factors. It’s the standard for normal crops that require normal wattage level at the vegetative stage.

  • 40 Sq. ft (6×7) – 1280 watts
  • 36 Sq. ft (6×6) – 1150 watts
  • 30 Sq. ft (5×6) – 960 watts
  • 25 Sq. ft (5×5) – 800 watts
  • 20 Sq. ft (4×5) – 640 watts
  • 16 Sq. ft (4×4) – 500 Watts
  • 12 Sq. ft (3×4) – 400 Watts
  • 9 Sq. ft (3×3) – 300 Watts
  • 6 Sq. ft (2×3) – 200 Watts
  • 4 Sq. ft (2×2) – 120 Watts
  • 2 Sq. ft (2×1) – 60 Watts

In short, different sizes of your grow tent will need different light intensity. Hence the reason why you need to choose different light per square meter. We will show you how to calculate the wattage for your different sizes of grow tents.

3. Type of LED Grow Lights

You must be aware that there are different LED lights you will find in the market. Different plants will need different grow lights. With the same Watts, plants will produce different yields when you use different types of LED lights.

When you think about the types of grow lights, the following are the key things you need to consider.

The color of your LED lights

The color spectrum is an important factor to consider when it comes to choosing the type of LED light. When you use different colors, your plant will give the same results. A White color won’t yield the same results as red or blue LED light.

Research shows that growing your plants with red LED light will lead to some sort of leaf deformities. To get the best results from a red light, you would need to mix it with a blue light to bring a pink effect.

A mix of Blue, Red, and white gives a pink light which is becoming an ideal design for most growers.

But if you want to get the best results from your grow spaces consider white LED or Multi-colored/Full Spectrum LEDs.

White LED lights are the closest to the natural sunlight. They give a good light intensity that your plants will thrive well under. And when you think about a White LED light, there is no other better light than the Miracle LED 100W Spectrum Grow Lite.

The only challenge with white LED lights is that they have too much green and yellow spectrum, which is useless to the plant. But to solve this problem, you will find the Multi-colored LED lights in the market. These are a combination of the lights that are needed by your plants.

They are commonly known as Full Spectrum LED grow lights. And the best of them are Advanced Platinum Series P300 300W 12-Band.

The Height of the Light

You might install any size of LED light in your grow tent. However, the watts needed for your plant will also depend on the height that you place your light over. With each difference in height, there comes a change in the amount of light received by your crops.

Height of the lights is a trick that you would also use for every phase of your growth stage. Instead of buying new LED lights at every phase, all you need is to adjust the height of your lighting systems. This would give you the best light intensity required by your plant.

If you are growing your plants from germination to harvest, its advisable to buy full cycle LED light.

Heat Output

Led lights produce some amount of heat as they operate. LED lights with low heat output gives the best results. This is because low heat reduces overheating in your grow tent. As a result, you won’t require cooling and your plants won’t be affected by excess heat.

Procedure for Determining Watts Per Square Foot for LED Grow Lights

We have already discussed the most critical factors that you need to consider when choosing a grow light. Now we are going to help you make a good decision on each of these factors. The main focus here helps you get the best light wattage for your Grow tent and plants.

Follow these simple steps and choose the best results.

Step 1: Measure the Size of Your Grow Tent in Square FeetMeasure the Size of Your Grow Tent in Square Feet

As we discussed earlier, the size of your grow space is a critical factor that will determine the wattage needed for your grow tent.

So, start by measuring the width of your area and multiply it with length. Once you get the total size, seek to buy lights with an intensity that matches the area.

Generally, under the size of your grow tent, use the same dimensions as we had previously share. The following are the light intensity for each size.

  • 40 Sq. ft (6×7) – 1280 watts
  • 36 Sq. ft (6×6) – 1150 watts
  • 30 Sq. ft (5×6) – 960 watts
  • 25 Sq. ft (5×5) – 800 watts
  • 20 Sq. ft (4×5) – 640 watts
  • 16 Sq. ft (4×4) – 500 Watts
  • 12 Sq. ft (3×4) – 400 Watts
  • 9 Sq. ft (3×3) – 300 Watts
  • 6 Sq. ft (2×3) – 200 Watts
  • 4 Sq. ft (2×2) – 120 Watts
  • 2 Sq. ft (2×1) – 60 Watts

Step 2: Choose Light Intensity Needed By Your PlantChoose Light Intensity Needed By Your Plant

Plants require different Photosynthetically Active Radiation (PAR) which is determined by the light intensity. It’s the light spectrum that your crop will need for photosynthesis.

In simple terms, it’s the measure of energy discharged by your LED light and used by the plants for growth.

Usually, the light is measured in micromoles per square meter per second (µmol/m2/sec) — the light consumed by your plants per second. The requirement of the light intensity also varies for plants at different phases of growth.

The following are the light requirements for optimum yield in every stage of plant development.

  • Seedlings – 200-400 µmol/m2/sec
  • Vegetative – 400-600 µmol/m2/sec
  • Flowing – 600-1000 µmol/m2/sec

When measuring the PAR of a LED light, the red, blue and green wavelengths are the primary factors considered – the light spectrum needed by your plants.

For good lighting, consider buying a full spectrum LED lights.

Advanced Platinum Series P300 300W 12-Band is the best full-time spectrum LED light you will find in the market today.

Step 3: Determine the Number of Plants in Your Growing Area

We already mentioned that the number of plants in your grow room would determine the light intensity they would require. If for instance, you are growing cannabis, there are particular styles that you must apply to ensure you get the best yield.

Different growing styles would also dictate the number of plants you grow per square foot; hence the reason in the difference in the light requirement for per the square meter.

The following are different styles of growing that will determine the plants you need per square meter.

Sea of Green (SOG) Technique

Under this technique, you will need to plant 4 to 16 plants per square meter. This technique covers the available space available in your grow tent. It also requires LED lights with a high wattage output.

The Screen Of Green (SCROG) Technique

Under this technique, you can only grow one plant per square meter. You weave your plant over a screen to utilise the grow space and get the best yield per plant. You don’t require a high wattage bulb in this case.

Topping (Pruning) Technique

You can only grow one plant per square meter under this technique. Much space is needed for pruning and allowing the plants to grow to bushes. Under this case, you will need power requirements as a SCROG technique.

Low-Stress Training (LST)

Under this technique, you will need to grow 4 plants per square meter. It’s a technique that trains plants to grow as bushes. You won’t require high wattage as SOG. However, the light requirement will be the same a Pruning and SCROG techniques.

Basically, good LED grows lights of 300 Watts can grow 1-6 plants comfortably. If you have more plants, you can add more LED lights and place them one side by the side of your grow tent.

However, the number of watt requirements increases per square feet, depending on the number of plants grown in the same are.

The following is a guide to the wattage you will need per square foot depending on the number of plants grown in the same area.

  • 12 plants per square foot – 340-380 watts
  • 10 plants per square foot – 300-340 watts
  • 8 plants per square foot – 240-300 watts
  • 6 plants per square foot – 180-200 watts
  • 4 plants per square foot – 120-140 watts
  • 2 plants per square foot – 60-80 watts
  • 1 plant per square foot – 30-40 watts

So, when calculating the entire grow tent watt requirement look at the number of plants per square meter and multiply them with the wattage requirement.

For example, if you have 2 plants in a 4 square feet space;

2×4 = total footage of 8 square feet.

A square foot requires 32 watts. So, for your tent you will need;

8 feet x 32 watts = 256W LED grow lights

The best thing about LED lights is that only 5% of the wattage goes to heat emission. 95% of the total watts goes to light energy. This means when you are choosing light, let it be powerful enough to provide power requirements for your grow tent.

Step 4: Chose the Right Height of Installing the LED Grow Light

The distance between the plant canopy and the lighting system has a direct impact on light intensity. So, having the right LED lights and placing them at the right heights is critical if you would wish to get the best yields from your plant.

Avoid keeping the LED lights too close to your plants. This will minimize the chances of bleaching, sunburn, nutrient deficiencies, and yellow coloring on the leaves.

There is no standard height for installing grow light for every plant. However, at every plant stage, you need to change the heights. During the germination place, the lights high above the plants. During the vegetation stage, lower them to a perfect height that will supply a good amount of light.

how many watts per square foot for led grow lights

Best LED Lights for Your Grow Tent

Buy either the following LED lights. Choose the lights that match your grow tent light needs. After calculating the entire light requirement for your entire tent, choose the lights that will give the wattage required by your plants.


  • Different Wattages available (1000W, 2000W & 3000W)
  • Out top pick
  • Powerful cooking system

King Plus LED Grow Light

  • Available in 600W, 1000W and 1200W
  • Comes with a bloom switch
  • Full-spectrum light
  • Energy-saving technology

Advanced Platinum Series

  • 300 watts
  • Superior 12-band full spectrum
  • Perfect for a 4×4 coverage at 18” height

Parting Shot

As we end, it’s important to remind you that there is no universal guideline for the watts needed per square foot for LED grow lights. The requirement of the light wattage differs on various factor.

To choose a LED light with the best light intensity, you need first to understand your plants, the size of your grow tent, nature of the lights, and height you need to install them. Once you are aware of all these factors, you will be in a position to get the best Watts per square foot.

Most importantly, ensure you buy the right LED lights that will distribute enough light intensity. Depending on the size of your tent buy the lights we have recommended in this article.