How Many Grow Lights Do I Need? | Step By Step Guide With Tips

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by Morgan

Last update:

January 16, 2023

How To Choose The Right Lighting For Your Marijuana Grow Room

Grow lights are the most critical and expensive part of your growing process, so the question "how many grow lights do I need?" must have clicked on your mind a few times. Without proper lighting, plants will not have the desired productivity. If you have plants growing for the first time, selecting the right to grow lights can be challenging. 

You'll want to provide your plants with plenty of light to grow appropriately when growing indoors. As the plant grows into its flowering stage, it doesn't need as much lighting. Therefore, you must choose the number of LED grow lights for your cannabis plants.

Different types of lights work well with varying numbers of plants, so knowing how many plants you need to light or which kind of grow lights you need for a head start is beneficial for an indoor grower. Continue reading to learn more information about optimizing your grow light setup.

Step By Step Guide: On Determining the Recommended Number of Grow Lights You Require

Understand Your Plants Requirement First

Understanding your plant's requirements is the only key to success. Depending on the type of plants, stage of growth, and canopy size, you need to determine how much light your plant needs per day. Secondly, the type of LED grow lights also matters a lot. Different types of grow lights emit different wavelengths of light required by the plants at various life cycles. For example, blue and white light waves stimulate growth during the vegetative stage, while red and orange waves help flowering and fruiting.

After determining all these factors, you need to calculate the total number of grow lights you need according to the size of your grow room.

Determine the Size of Your Grow Room

After you determine how many plants you will be growing and the type of light they need, the next step is to calculate the size of your grow space. The size of your grow room will directly impact the number of LED lights you need.

A general rule of thumb is that one square foot of space should have at least forty-two watts of light. A four-by-four grows tent would require six sixty-six-watt CFL bulbs or two-three hundred thirty-five-watt LED grow light.

Consider the Wattage of Your Lights

After understanding your plant's requirements and the size of your grow room, the next thing to consider is the wattage of your lights. Not all grow lights are created equal and come in various wattages. Higher-wattage bulbs will produce more light but will also cost more to operate.

A sixty-six-watt CFL bulb, for example, generates roughly the same amount of light as a one-hundred-and-fifty-watt HPS lamp while using less electricity. A 350-watt LED panel may produce more light than either of those options, but it will be much more expensive upfront.

Choose the correct wattage according to your budget and needs.

Determine The Coverage Area of Your Lights

The coverage area is the amount of space your lights can effectively cover. It's important to consider because you don't want to waste money on lights that are too powerful for your room or end up with insufficient light. 

To determine the grow light coverage, take an example; a three hundred fifty-watt LED light might have a coverage area of four-by-four feet, while a one hundred fifty-watt HPS light might only cover two by two feet.

Calculate the Total Number of Lights You Need

After considering all the factors, it's time to calculate the total number of lights you need for your room.

You will need one light for every square foot as a general rule. However, this number will change depending on the type, grow light wattage, and the size of your grow room.

For example, if you have a ten-by-ten grow room and use sixty-six-watts CFL bulbs, you will need forty bulbs. However, if you use three hundred fifty-watt LED panels, you will only need four lights because they have higher light intensity.

Research Your Plants Specific Lumen/PAR Needs

Before determining this, you will first need to understand what Lumen and PAR Are;

A lumen

It is the unit of measurement that tells you how much light is emitted from a bulb. The higher the lumen, the brighter the light.


PAR or Photosynthetic Active Radiation is the range of light used by plants to create energy through photosynthesis. This is the most crucial factor to consider when choosing to LED lights because it will directly impact the health and growth of your plants.

Now that you know what these terms mean, you can research how much light your specific plants need to thrive. This information can be found online or by asking your local nursery or garden center.

plants under the grow lights

Once you have this information, you can use it to determine how many lumens or PAR your grow room needs per day. To resolve this, first, you need to calculate the square footage of your grow room and then multiply it by the number of hours of light your plants need per day. For example, if you have a ten-by-ten grow room and your plants need eighteen hours of light per day, you would need eighteen hundred lumens or PAR.

Choose the Right Lights for Your Grow Room

Now that you know how many lights you need, it's time to choose the right ones for your grow room. There are a variety of LED grow lights available on the market, so it's essential to do your research before making a purchase.

To help you get started, here is a list of some of the most popular grow lights:

  1. CFL- Compact Fluorescent Light bulbs are one of the most popular types of LED lights because they are inexpensive and easy to find. They are also relatively cool, so they won't overheat your grow room.
  2. HPS- High-Pressure Sodium bulbs are another popular option because they are very efficient and produce a lot of light. However, they require a bit more ventilation than other lights because they generate a lot of heat.
  3. LED- LED Lights (Light Emitting Diodes) are becoming increasingly popular because they are very energy-efficient and long-lasting. They also produce very little heat, ideal for small grow rooms.

Install Your Lights

Once you have chosen the right lights and you know how many grow lights you need., it's time to install them. The installation process will vary depending on the type of grow light you choose, so follow the instructions with your lights.

You will want to hang your lights from the ceiling or a stand to be at the correct height above your plants. You will also want to make sure that your lights are evenly spaced throughout the grow room to ensure that all of your plants receive an adequate amount of light.

Finally, you will need to plug your lights into an outlet and turn them on. Start with a low setting and gradually increase the intensity as your plants become acclimated to the light.

What Is the Coverage Area of a Grow Light?

The size of the area that a grow light can cover will depend on the light you are using. For example, a CFL bulb will only be able to light a room of about four square feet adequately. On the other hand, a LED panel can often provide enough light for an area of up to ten square feet.

When deciding how many LED lights you need, it is vital to consider the size of the area you are trying to cover. If you are only looking to light a small space, then a single LED grow light may be sufficient. However, if you want to cover a larger area, you may need multiple lights.

plants in the grow room

It is also essential to consider the type of plants you are growing. Some plants require more light than others. For example, plants that flower or fruit, for instance, growing tomatoes, will often need more light than leafy greens. As a general rule of thumb, you should aim to provide about 30 watts of light for every square foot.


How Many Grow Lights Do I Need for One Plant?

The number of grow lights you need for one plant will depend on the size of the plant and the type of light you are using. For example, a small plant might only need a single CFL bulb, while a larger plant might need multiple LED panels.

How Many Grow Lights Do You Need for Six Plants?

The number of grow lights you need for six plants will depend on the size of the plants and the type of light you are using. For example, if you use CFL bulbs, you might need six bulbs to light all plants adequately. However, if you use LED panels, you might only need three panels.

How Many Grow Lights Do I Need for A 4x4 Grow Tent?

The number of LED lights you need for a 4x4 grow tent will depend on the type of light you use and the plants you are growing. Generally, you should provide about 30 watts of light per square foot of growing space. For a 4x4 grow tent, you need a light with at least 480 watts.

What Is the Coverage Area of A 1000-Watt Grow Light?

Such a LED grow light covers an area of up to 100 square feet. However, the number of plants you can grow in that space will depend on the type of plants you are growing and their light requirements.

How many watts and Grow Lights Do I Need for Vegetables?

The light coverage required for vegetables will vary depending on the type of vegetables being grown and the time of day. In general, 30 watts of light for every square foot of growing space is a good target.

If you want to cultivate leafy greens, you might need one CFL bulb. If you're growing fruiting plants like tomatoes, though, you might need more than one LED panel.

What Type of Grow Light Is Best for Vegetative Growth?

The LED grow light that is best for vegetative growth will depend on your specific needs. However, some types of lights commonly used for vegetative growth include fluorescent, HPS, and LED lighting.

It's Not Just the Number of Grow Lights - Area Size Should Be Considered

The quantity of lights you'll need is determined by the amount of the area you're aiming to cover and the sort of plants you're growing. As a general guideline, you should offer 30 watts per square foot of growing space. 420 Green Thumb can assist you if you are new to farming and want to learn more about grow lights. 

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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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