How High Should Grow Lights be Above Plants?

If you’ve spent any time searching for the best height to hang your grow lights, you’ve probably found a bunch of wildly different answers.
That’s because it’s impossible to give an exact distance.What I can give you, is a good starting point.

From there, you’ll gradually move the lights closer to the canopy, while monitoring your plants closely. This way, you’ll end up finding the sweet spot for your particular garden.
That’s the best anyone can do for you. The perfect hanging height depends on so many factors that no one could ever provide an accurate answer.

But if you follow the recommendations below, you will have no trouble finding the perfect distance to hang your grow lights above your particular canopy.
We’ll begin with LED grow lights, then we’ll cover HID lights, then fluorescent lights, and finally ceramic metal halide.
Why do different grow lights need to be hung at different heights?

If your indoor garden is supposed to mimic a plant’s natural (outdoor) environment, then the grow light is the sun from which everything grows- only you have control over what type of light and how much of it your plant receives. That’s partially why growers say more light=better yields. But does that mean you should get more lights and hang them as close to your plants as possible without touching them?Of course not.It means making sure they receive enough energy to grow quickly without overpowering them. But to assure that your plants are getting exactly what they need- no more, no less- you’ll want to check the type of light you’re giving your plants: L.E.D., H.I.D., or T5 Fluorescent lighting. Some lights offer more heat energy, and others offer better spectrums, and each needs to be hung in a different distance from your canopy:

LED grow lights, for example, need to be hung farther away from your plants than HPS/MH grow lights to avoid bleaching the canopy of your grow room from strong spectrums.

On the other hand, T5 Fluorescent lights need to be hung closer to plants than HID’s in order to have an effect on them because the energy coming from T5’s isn’t strong enough to get plants growing when hung from a distance of more than 12″.
Metal Halide & HPS Grow Lights

HID grow lights like Metal Halide and HPS (High Pressure Sodium) are the most widely-used and debatably the highest-yielding grow lights available for growing cannabis.

Metal Halide lights are well-suited to the vegetative stage and tend to encourage plants to grow short and squat though they are less electrically efficient than HPS. HPS lights are suitable for both the vegetative and flowering stage of cannabis growth and the light they give off encourages plants to quickly grow tall and produce big buds. Despite these differences, MH and HPS bulbs need to be kept about the same distance away from your plants. The proper distance actually depends on the size/wattage of your lamp.

HID Light Distance From Plants: Chart




150W – covers 2′ x 2′ (0.6m x 0.6m) area


250W – covers 2′ x 2′ (0.6m x 0.6m) area up to 2.5′ x 2.5′ (0.8m x 0.8m)


400W – covers 3′ x 3′ (0.9m x 0.9m) area up to 3.5′ x 3.5′ (1m x 1m)


600W – covers 3.5′ x 3.5′ (1m x 1m) area up to 4′ x 4′ (1.2m x 1.2m)


1000W – covers 4′ x 4′ (1.2m x 1.2m) area up to 5′ x 5′ (1.5m x 1.5m)
CMH Grow Light

CMH lamps are recommended for universal positioning. This means they can be positioned vertically or horizontally above the canopy. The position won't cause damage to the bulb.


The position won't affect the light distribution, and every plant will have a consistent absorption rate. The grow light must be hanged minimum 3ft above the canopy to avoid any hot spots. This also provides an efficient and even light distribution.


The light distribution is so intense that a bulb with 315W can have a coverage area up to 4ft x 4ft. This is larger than what higher wattages MH and HPS bulbs provide.


An increase in the watts leads to a bigger coverage area. The higher watts contribute to greater heat produced. Make sure you hang the grow lights at least higher than 3ft above the plants to cancel out the effects of the heat.


The table below shows the recommended coverage of each CMH bulb and the distance from plants you should keep.



LED Grow Lights

I know most of you are using LED grow lights and unfortunately, those are the hardest lights for which to estimate an ideal hanging height. There is just so much variance in the output of different LED brands.


They are also deceptively strong, especially the red and blue mixed lights (i.e. not the all white LEDs).


The light looks dim and it doesn’t feel very hot, but it can scorch the plants nonetheless. For this reason, you want to keep a close watch over your garden, whenever you start using a new light, until you get a feel for the ideal grow light height above plants.


Most manufacturers provide the recommended hanging height for their lights.


If that is the case for your light, start with your light hanging at the distance they recommend. Watch your plants closely and back the lights off if their are any signs of bleaching (i.e. the leaves begin turning white).


If the plants are fine, move it a bit closer until you reach the point where they begin to bleach the leaves. Then back them off again and you have your ideal height (for flowering; for vegging, back it off 6 to 18 inches more).

If you do not have a recommended height for your light, start by hanging it according to the chart below, depending on the strength of your light.

The wattages are HID equivalent, not actual LED watts, meaning a 1000 watt light in the chart below will actually consume between 550 and 700 watts.

Note that these hanging heights are for the highest quality lights with extremely powerful LEDs. If you get a lower cost LED grow light, you’ll probably need to hang it closer (but you always want to start higher and slowly lower the lights).

LED Grow Light Distance Chart


Fluorescent Grow Lights

Fluorescent grow lights give you a nice, easy blend of energy and spectrum output. They effective enough to grow nearly any plant, but to do so, you’ll need to hang them pretty close.

What makes hanging fluorescent lights so tricky is that not all of them are the same. For instance, CFL bulbs can generate some decent heat over an extended period of time because of their compact size, whereas a longer 54w 2ft T5 grow light won’t generate lots of heat because it can dissipate it along its tube. Not only that, but the more bulbs you use the more heat you’ll generate, which is dangerous if it’s hung too close to the plants.

Fluorescent lighting isn’t known for kicking off lots of heat, but they will generate some heat while they run so you’ll need to watch your plants carefully for signs of burning or bleaching.

In general, you’ll want to hang your light no more than 12″ away from your plants.

This one’s not an exact science, unfortunately, because fluorescents come in different shapes and sizes. That said, we recommend the following:

– Start out at 5 inches above the canopy

– Compact CFL bulbs usually generate more heat than a long T5 grow lights, so measure the canopy temperature to assure you’re at a safe level to grow

– If canopy temps are too high, raise the light another inch and check the temp again

– Raise if the temps are too high, lower if the temp is too low

– Remember: after 12″ fluorescent lighting loses its power, so make sure you don’t raise it any more than 12″ above your canopy otherwise your plants aren’t getting light energy.