# What size room can a 400 watt mh/hps sufficiently light?



## KP419 (Dec 7, 2012)

What size room can a 400 watt mh/hps sufficiently light? I am really not great at calculating Sq. ft so if someone could provide an answer like 4x4 or 6x8? thanks that way just makes it easier for me!


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## Locked (Dec 7, 2012)

KP419 said:
			
		

> What size room can a 400 watt mh/hps sufficiently light? I am really not great at calculating Sq. ft so if someone could provide an answer like 4x4 or 6x8? thanks that way just makes it easier for me!




It looks like typical 400W MH bulbs put out between 33,000-36,000 lumens. So if we go with 36,000 you could use it for up to 12 sqr feet of veg space. If you wanted to flower with it for some reason it would be good for 7 sqr feet.


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## powerplanter (Dec 7, 2012)

3x2 or 3x3 give or take.


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## Herm (Dec 7, 2012)

IMHO as I grow more I find the depth of canopy supported by the light tends to be more important than the size of room.


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## KP419 (Dec 7, 2012)

My new room is 4x7x6...(4ft wide 7ft in length and 6ft tall) what is the square ft of this room and what size light would i need to run? I know I am going to have to partition a part of this room off since I only have a 400 watt at the moment.


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## Growdude (Dec 8, 2012)

KP419 said:
			
		

> My new room is 4x7x6...(4ft wide 7ft in length and 6ft tall) what is the square ft of this room and what size light would i need to run? I know I am going to have to partition a part of this room off since I only have a 400 watt at the moment.


 
4x7 = 28 square ft.
28 x 5000 lumens = 140,000
140,000 lumens = 1000 watt HPS

A 400 watt HPS will give you ~45,000 lumens. or 9 square ft.


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## pcduck (Dec 8, 2012)

a 400 hps rated at 60,000 lumens will cover 12 sqft a 3x4 room.


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## BackWoodsDrifter (Dec 8, 2012)

Not much good at the calculatin either pilgrem but I can answer like this here ifin it helps. I can grow 3-4 plants quite nicely under my 400w mh but then gain I have a couple 150w hps in the mix as well. Good luck yur travels pilgrem hopes they end well with yur pouch full 

BWD


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## KP419 (Dec 8, 2012)

do you think if a minimize the room to 4x4 will my 400 watt do ok?  I am going to do my first scrog grow this time. I always have issues with one or two plants growing much taller and faster than the others and constantly having to either move the light or the plants so going to give scrog a try as I have seen others have great success using this method. How close can I keep my light from my plants without damage? I have an exhaust fan on top on my ballast to remove the heat the lights gives off.


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## pcduck (Dec 8, 2012)

how many square feet are in a 4 x 4 space?


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## Locked (Dec 8, 2012)

KP419 said:
			
		

> do you think if a minimize the room to 4x4 will my 400 watt do ok?




No, I do not.   50,000 lumens, which is what a 400W HPS will bring to the table, is only good for up to 10 sqr feet in flower. You will have 16 sqr feet in a 4x4 area. 3x3 would get you in the ball park.


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## The Hemp Goddess (Dec 8, 2012)

KP419 said:
			
		

> do you think if a minimize the room to 4x4 will my 400 watt do ok?  I am going to do my first scrog grow this time. I always have issues with one or two plants growing much taller and faster than the others and constantly having to either move the light or the plants so going to give scrog a try as I have seen others have great success using this method. How close can I keep my light from my plants without damage? I have an exhaust fan on top on my ballast to remove the heat the lights gives off.



No.  To get the area of a room, all you need to do it to multiply the length and the width--very basic math.  A 4 x 4 is 16 sq ft and a 400W light will not cover that much.  You are going to want your space 9 or 10 sq ft, depending on the lumens from your bulb.  A 9 sq ft space is 3 x 3.

What do you mean when you say you have an exhaust fan on top of your ballast?  Can you explain your ventilation system? What type and size of fan you are using?


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## KP419 (Dec 8, 2012)

I was adding the info on exhaust because of the heat in such a small room. There is a vent on the very top of my light with a 15ft exhaust hose ran into my crawl space and I just have a basic square bathroom exhaust fan at the moment that fits perfectly over the vent and works great, room is never to hot. I am going to be getting a new light after this grow because obviously a 400 watt doesn't do much. Thanks for explaining the sq ft. thing, i feel dumb now knowing how easy that was, simple mathematics. How many sq ft can a 600 and a 1000 watt light each cover? I want to upgrade to a bigger light.


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## pcduck (Dec 9, 2012)

> i feel dumb now knowing how easy that was, simple mathematics. How many sq ft can a 600 and a 1000 watt light each cover?



600 watt bulb lumens divided by 5000 lumens equals the square footage a 600 watt bulb will cover. EX: 95,000 lumens divided by 5000 equals 19 square feet is what a 95,000 lumens 600 watt bulb will cover.

1000 watt bulb lumens divided by 5000 lumens equals the square footage a 1000 watt bulb will cover. EX: 155,000 lumens divided by 5000 equals 31 square feet is what a 155,000 lumens 1000 watt bulb will cover.

I used DigiLux Bulbs for these examples


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## KP419 (Dec 9, 2012)

thanks to everyone that helped me out here, now i have a better understanding of lumens and sq ft.


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## Locked (Dec 9, 2012)

KP419 said:
			
		

> thanks to everyone that helped me out here, now i have a better understanding of lumens and sq ft.




Glad we could help get you on the right track...:icon_smile:


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## OldDaddyFedder (Dec 9, 2012)

KP419 said:
			
		

> My new room is 4x7x6...(4ft wide 7ft in length and 6ft tall) what is the square ft of this room and what size light would i need to run? I know I am going to have to partition a part of this room off since I only have a 400 watt at the moment.


 
Also, you have 168 cubic feet of space, so you will need 150-200 cfm fan for ventilation.
Thought I'd throw that in.

:48:

ODF


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