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.
Contents
LED Grow Lights Distance From Plants
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
Metal Halide And HPS Distance From Canopy
For HID grow lights, you can use the “back of the hand” test as a general rule.
Simply hold your hand just above your plants where they are closest to the light, with the back of your hand facing the light source. Hold it there for about 30 seconds.
If your hand starts to get too hot for comfort, then the light will be too hot for your plants as well and you want to hang it higher. If your hand could be closer and still not feel discomfort, go ahead and bring the light closer.
You want your hand to get hot, but not unbearably so.
To get an idea of how high to hang you light to start with, consult the chart below. I’d always begin with the light at the upper end of the range and gradually lower it.
So, for example, a 1000w HPS distance from plants for bloom would start at 36 inches and gradually move closer.
T5 Grow Light: Distance From Plants
Fluorescent lights don’t get nearly as hot as other types of lighting, so you can get them extremely close. In fact, as long as they are not touching the plants, you should be fine (with mature plants).
You can use the same hand test I described above in the MH and HPS section to see if the light is too close or not. To begin with, hang it about 4 to 6 inches above the tallest plant, for vegging or flowering.
The T5 fluorescent grow light distance for seedlings should be a bit further away.
I’d start by hanging the light 6 to 10 inches from seedlings. Use the same distances whether you are using a large T5 fixture or just a regular fluorescent light bulb.
How High Above The Plants Do I Hang Ceramic Metal Halide Lights?
You can use the same hand test described above with ceramic metal halide grow lights to determine the best hanging distance. To begin with, start by hanging the ceramic discharge MH lights two feet above the canopy.
That is the standard hanging distance for a 315 watt CMH light (which is most of them). For the 630 watt (double bulb) fixtures, you can go ahead and start them at the same distance.
How Far Grow Lights Should Be From Plants: Final Thoughts
How high to hang your grow light depends on a lot of factors. We tried to cover the most common ones in this article and give you a good idea of which height to start at. You can then adjust from there.
If your grow light comes with recommendations for a hanging height, that will probably make a better starting point. Hanthe light at the recommended height above the canopy and adjust based on the results.
Pedro Cardoso says
Hello my name is Pedro
My question is ,
What’s the range in square meters of a 600 and 1000 watts HPS bulb?
Thank you for your attention
Kind regards
Pedro
Steven says
Generally a 600 watt bulb covers around 1.2 x 1.2 meters and a 1000 watt bulb covers around 1.5 x 1.5 meters.
Anonymous says
My 600 covers 5×5
Anonymous says
BUNK THO…….I GUARANTEE
Anonymous says
BUNK WEED
Michael says
Hello, I have these LED clip on “Strips” it looks almost like a desk lamp, but there are two heads and a long strip with the Red and Blue LED lights, (I am trying to grow cilantro for my wife), I have the light about 15 inches away and they grow like anything in the beginning (One week and had sprouts, 2 and they were already a inch or so up) but after a month they seem to have slowed down, I am not sure if its the organic seeds or the light distance, I have the lights on a timer and have them on 15 hours a day (I tried growing other things like Radishes, but in 40 days they grew great on top but no radish under the ground. Not sure what is going on, I usually grow outside in the dirt, but I can not anymore. Any suggestions. Thank you very much.
Steven says
I’ve grown cilantro on a windowsill and it always grows really fast in the beginning. If yours gets some natural light too, it’s probably not an issue with lights, but with something else, like pot size, soil, etc. If the LED is the only light your plants get, it may just not be powerful enough for the plants once they get larger.
Michael says
Thanks Steven, yes, the LED’s are the only direct light it gets, it of course gets a little light from the window it is close, but all of my windows face north, so no sun directly comes in that is why I am using the lights, Also maybe it is the cilantro as I looked I have planted “Organic” when I think I use to use regular. Thanks again
Steven says
If there’s a window, then the lights are definitely strong enough. Even if they’re not getting direct sunlight, they’re still getting light. And cilantro doesn’t have huge light requirements.
Michael says
Well it has only been 5 weeks and they are starting to make the second level that they do, so maybe the LED’s are working, but I think I will lower the LED time down to maybe 10 hours and open the drapes more. (I live in Las Vegas and the sun is VERY hot, so normally opening the drapes next to the plants is a no, no if I want to keep the house cool as this last week we have been over 110.
Debbie says
I have some indoor plants that are about 5′ tall 5″ and I bought a 4′ 32 W full spectrum led grow light to put them down in my basement. I’m trying to figure out how far off the plant I should hang my light however I have not seen one that is only 32 W. I hope that is strong enough to just keep my plants growing normally.
Steven says
I don’t know what kind of plants these are or how much natural light they’re getting, but I highly doubt that light is going to be even remotely strong enough for several plants of that size.
You can hang it quite close, since it doesn’t have too much power, but then it wouldn’t cover all of the plants.
Michael says
My growing cilantro was a total bust, which was sad for me. I have a old Aerograden which just uses the plant food and “moss” type growing medium and they are in the water 24/7 and they grow great, so I thought why can’t I grow plain Cilantro in dirt in a huge pot inside with a grown light, nope they grow great for the first 2-3 weeks, nice, green and straight, then the rest of the time and before harvest they shrink, turn yellow, and almost die, I check the soil with a moister meter, and keep the light on pretty much as much time as the Aerogarden did, but nothing. Not sure how to do this, I mean how do pot growers do so well when I see them on TV news when they bust a place.
Steve says
Check the pH of your soil.
If you’re feeding your plants with a Miracle Grow type fertilizer, the pH is likely too low which will cause the nutrients to get locked in the soil.
Robert says
I have a 315CMH light in a 3×3 tent, and I keep the canopy at 18″ after I start bloom and about 20″-22″ during VEG.
Steven says
That sounds about right.
Carol Roehrs says
I would be extremely cautious about this retrofit. If the fluorescent ballast and the lamp are not compatible with each other you run the risk of sub par performance and potential fires. Believe me, this is not worth the risk. If they are compatible, then it will work well enough.
Steven says
I think you may have put this comment on the wrong article…
Hugh Johnson says
Shut the fuck up you stupid bitch
Who cares says
Lmao !!!???? So random and ignorant
EfkaOg says
Hey i have 30W led light 2550 lumens color is 6500k cold white led type SMD, how close can i place it to one plant in veg?
Steven says
As close as you want, I’d say. A 30 watt light isn’t going to damage anything. But if you do start to see damage on the leaves, move the light back.
Sally Apple says
What does cm mean?
Steven says
In what context? I don’t see CM used anywhere in this article. The closest I see is CMH, which stands for Ceramic Metal Halide.
Anonymous says
cm = centimeters
Steven says
That is true, but “cm” doesn’t appear in the article, so I don’t think that’s what she was asking. But she never clarified, so I guess she figured it out.
Donald Anselmi says
Sorry for not being clear earlier. I bought these gorw lihgts, but the directions aren’t that clear on how to start them with seedlings and how to proceed once the vegetable starts to grow. I am trying lettuce and kale. Would love any of your helpful thoughts. Thanks!
Joseph M. Gates says
Good afternoon,
I have a 50 W LED grow light that I purchased on eBay and I don’t see any measurements for that up. Your chart stop said 200 or starts at 200. So I’m wondering if I should make it mine closer. I have a Christmas cactus that I am nursing a long from a previous growth. I don’t want to lose it.
Any suggestions on how close that should be would be appreciated. Thank you
Steven says
You can generally put a light like that as close as you want. If you do see some damage start to appear on the cactus, back the light off.
David says
I have a 400w self ballasted T5HO light fixture . How close should they be hanging above my canabis plants
Steven says
You can hang these within a few inches, but if you’re vegging you probably don’t need to get that close. Just hang it where it adequately covers the whole are of your plants.
Jason says
I only have a 9 w full spectrum led bulb. I read in other questions that it doesnt matter how close I place them too my plant, My question is with it being a full spectrum bulb does that change the distance i should hang my bulb from my plant?
Steven says
No. 9w is not powerful enough to do anything.
Anonymous says
I’v burned plants with a 9w led bulb. I now keep it about 8-12 inches away. They are still intense light compaired to floresenent.
your mom says
nope
Scott says
Hey. Thanks for all the info! I have two 1000W led lights to put over some lime and lemon starter trees. Looks like I need to be a few feet off the top of the tallest. The cabinet I made won’t allow that height. Sounds like I need a lower power light for fruit and only being a foot over the tallest. What do you think? Thanks again!
Steven says
If you have the lights already, give them a try. Just watch the plants closely. If they start to burn, you’ll know the lights need more space. Or you need less powerful lights.
Greg Woodward says
I have a 600 watt Full spectrum LED. I’m lighting 2-4 small to medium ficus and elm indoor Bonsai trees.
I started 30 Inches away . Do you think that is a good starting point? How do you know when to leave the light alone or the need to move closer. How long generally does it take to see issues
Bob K says
Hi, I have a indoor miniature rose bush which is lighted with a 23 watt 6500K bulb, what distance should the plant be from light?
Thanks, Bob K.
Btad C Cobb says
I have 50 watt full spectrum. Lights over my vegging plants at 24 in Is that good enough height or do they need to be lowered?
Scott Harr says
I have a 64 white tea 15 LED red Full spectrum light how far should I Placed my lights above my plants
I start to see some tinging on my leaves but I’m not sure if that’s from low light that I had before or if it’s from these new lights
Steven says
You should be able to get this light fairly close. Just watch the plants carefully over the next few days. If the discoloration gets worse, move the light higher. If there’s no change, you can leave it where it is.
If you move the light back and you’re still seeing the leaves get worse, it’s probably due to something else, not the light.
Anonymous says
Sorry 64 watt T15 Red full spectrum
Donald Anselmi says
I have 72 watt LEDs. They are 144 PCS LED.. This is the first time I’ve done seedlings. My lettuce and kale have already starting coming up after 3-4 days under the lights. The lights were really close before the popped up. The lights are in full power but can be dimmed. I have the lightS about 10 inches above the seedling now that they have germinated. How far should the light be above them? Lots on the web and confused. Thanks so much for this space with questions!
Steven says
It’s never really possible to answer these questions, since it depends on so many things and is always different. That’s even more true, with no real info on the light.
The only way to know where the light should be is to test it yourself. If it’s not burning the plants where it is now, and they’re growing fine, then it’s good. If it starts burning them or they are not growing, adjust the height. Keep adjusting, until you find the perfect distance, then remember it for future grows.
Colby says
I am growing with 54 w t5 and and growing a autoflower how far should my light be I’m prob mid flower rn
Freddy says
I have a ge 40 watt 24 inch grow light how far do I need to be on seedlings an foe many lights would I need for a R by 4. Space
your daddy says
if u want super fast growth cut a hole in top of closet and have no carpet and a cracked window in Ur room for natural co2 outside air to flow while keeping humidity decent . place plants that are small enough in a clear 6 inch high 8 inch by 18 inch long tote so u can spray it for humidity daily . then place a fan in between so it blows straight up from the ground to the hole in ceiling. place cfl SPIRAL bulbs 5000 k and 6500 k close with in 4 inches as soon as new growth shoots up ( typically daily) u move the light above it about an inch every day or two should be newer growth if not Ur environment or light is off and should adjust until u get fast growth this way. . doing this i had clones to bush for bloom every 30 days or less in 4 gallon tall pots