Grow Light Distance Chart: How far should my Grow Light be from my Marijuana Plants?

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by Morgan

Last update:

August 29, 2023

How To Choose The Right Lighting For Your Marijuana Grow Room

How far you hang your grow light from your marijuana plants depends on the power, wattage, and size of your grow light. You should always find out the wattage and the distance specified for the grow light before using it using a grow light distance chart (see below!). This way, you can ensure you get the maximum yield and potency from your plants.

In most cases, the grow light manufacturer will specify the distance grow chart on the packages, so read your directions carefully! If you already threw away the packaging, a quick google search will save the day — simply search for your light manufacturer + light wattage.

If you still doubt the distance to hang your LED grow lights, choose a distance based on the info below and watch them daily for signs of bleaching, then back the lights off or change the light’s proximity to the plants when you notice any.

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Here is a simple LED Grow light distance chart to help you

Grow LightClosestSunlightFurthest
150W8″ (20cm)10″ (25cm)12″ (30cm)
250W10″ (25cm)12″ (30cm)14″ (35cm)
400W12″ (30cm)14″ (35cm)19″ (48cm)
600W14″ (35cm)16″ (41cm)25″ (64cm)
1000W16″ (41cm)22″ (55cm)31″ (79cm)

How far should grow lights be from a marijuana seedling?

You should always regulate the heat and light intensity of marijuana seedlings. Place your marijuana seedlings 6-12 inches away from the grow light. You can double the distance of the grow light as your plants mature and grow more leaves. 

What happens if I place my grow lights too close to my cannabis plants?

When you place the grow light closer to your cannabis plants, they are likely to bleach. The plant leaf will burn if they are placed too close to the heat of the bulbs and are getting too much light. They can also start drying soon after the flowering stage, and this affects your yield and potency. Thus, it may not be the best quality for various uses of cannabis plants. Always use the indoor grow lights as recommended by lighting experts. 

Can you leave grow lights on 24 hours a day?

No, you should not leave the grow light on for 24 hours a day. Knowing how much daily light integral (DLI) your marijuana plants require is an essential step in ensuring you have a healthy grow op. Marijuana plant seedlings need some dark cycle to mature well. In general, plants also ‘rest’ in the dark period and use this time to take a break from growing and extracting nutrients from the soil and extremities. Therefore, you should give your marijuana seedlings at least 12 hours of light intensity and switch off the lights for the rest of the day.

Which is the best light colour for plant growth?

Plants need light intensity to achieve different growth goals. For vegetative growth, marijuana plants will require blue light. Blue light combined with red helps the plants to flower. If you are cultivating your flowering plants indoors, you should expose them to fluorescent bulb lights.

You can add or remove some grow lights depending on the stage of plant growth. Although blue and red are the most important colours for plant peaking, other colours are also useful to the plant. Sunlight is a combination of several colours, that is why plants exposed to sunlight grow healthy at different stages.

Will any LED light work as a grow light for indoor plants?

Yes, LED lights can work as a light for indoor plants. Most people prefer using LED lights because they are energy efficient. They also emit a lower amount of heat and white light, which means you can use them as grow lights. White light contains a mix of colours which is great for plant growth. 

The only downside of cheap LED lights is that they can easily damage, cause burns to plants when you don’t position them well. Also, there is a lack of standard specs from various LED grow lights manufacturers. 

Can you use regular bulbs as grow lights for plants?

Grow lights are more expensive than regular bulbs. Yes, you can use regular bulbs as grow lights in some cases. Generally, you should use regular grow bulbs for an indoor plant. However, if your plants are not getting enough light, you can change to grow light for the best results. Regular bulbs are most likely not the best thus it would be ideal if you can manage to buy the recommended grow lights. 

How do you know if your plants are not getting enough light?

You can tell if your marijuana plants are not getting enough light by checking a few factors:

  • The plant will be taller with weak stems as it strives to get closer to the light.
  • The leaves will be a bit light in colour because they will be lacking chlorophyll, which is a key component of photosynthesis.
  • The plant will form new broad leaves, and the plant’s inner part will turn yellow.

If you are growing marijuana indoors, consider bringing the light source closer to your plant.

How far apart should grow lights be from each other?

You should always space your grow lights 4 inches apart. However, the distance from each bulb will vary depending on the size of the bulb and the grow light wattage. You can also change the distance to the plant as the canopy changes. 

What should I consider when shopping for grow lights?

When shopping for grow lights, you should know where you plan to use the lights, how many seedlings you are planning to grow, and what kind of lights you need. For normal plant growth, you may need a traditional fluorescent bulb or energy-efficient LED lights. 

Are our house lights good for plants?

It is highly unlikely that your house lights will be good for your cannabis plants. If you no longer use halogen or incandescent bulbs, it is unlikely that the light intensity in your house will be enough for the plants. The light in your house is not designed to provide the spectra that marijuana plants require for growth and development. 

How much is an indoor grow light?

How much you pay for a normal grow light depends on the brand you want and wattage. A 24-Watts LED T5 tube costs $25, and a 54-Watt HID T5HO fluorescent tube may cost up to $5.20. You are likely to spend more if you are buying grow lights for vegetative and flowering phases. For instance, it costs up to $1,524 for a 630- Watts LED grow light used when marijuana plants are in the flowering stage. 

Which are the best grow lights for marijuana plants?

The best grow lights for marijuana plants are HID, fluorescent bulbs, and LED grow lights. Fluorescent bulbs are the best for small grows and compact plants. Quantum-board LED lights are energy-efficient and therefore save you on electricity costs (see quantum boards by MARS).

Know you know how far your LED grow lights should be from your marijuana plants

You should place your grow lights at least 12 inches away from the plants. If you want your indoor cannabis plants to grow healthy, place the grow lights within the recommended distance and choose the right LED, HID, and fluorescent bulb for the task. 

Not every bulb you buy can be used as a grow light. Therefore, you should find out if the bulb is rated as grow light before buying it. Place the lights at least 4 inches apart, keep watching the leaves, and adjust the proximity to the plant as they mature. Now you know what it takes to use the best LED grow light for marijuana plants.

Chart Source From: 


1. How far from plants should a grow light be?

LED grow light should be between 12 and 30 inches from the ground. Be mindful that the height of the lights may need to be different than the height of the growing plants, and it might change depending on the wattage of your lights, the plant variety, and the ambient light level.

2. Should I leave a grow light on 24 hours?

In general, it’s best to not leave lights on 24/7. Plants need darkness to develop properly. It’s believed that they really do rest during periods of darkness, and probably use this time to relax and move nutrients to their position in order to grow.

3. Can plants get too much artificial light?

Indoor plants typically require an hour to 12 hours of artificial fluorescent light to flower properly. If the light is too bright, plants will grow spindly and if they have too much light they will dry up and wilt.

4. Can LED lights burn plants?

LED lights are not harmful to plants. LED stands for light emitting diodes, which is a type of semiconductor that produces white light. The only potential way that plants could be harmed by the use of LED lights would be if they were in the direct line of sight with an intense beam and it was strong enough to burn them.

5. How many plants can a 1000W LED light grow?

As such, it can cover up to four plants with a 1000w grow light. Yield Lab 1000W HPS+MH Cool Hood Reflector Grow Light Kit (Price: $239.95) — With a 1000w grow light, you will receive a total lumen measurement of 130,000 from an HPS bulb and 110,000 from an MH bulb. So you are able to cover up to six plants with a light like this.

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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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