# grow room watts per foot ratio



## viper (May 11, 2009)

The number of plants in the list below is an approximate maximum number you can grow with various wattage mh or hps grow light systems. It is not exact, but it should give you an idea of the area a grow light can cover, and the number of marijuana plants that can be grown in that area. 

*A 250 watt* fixture will supply enough light to cover a 2.5 foot by 2.5 foot grow area. (6 plants or less)
*A 400 watt* fixture will supply enough light to cover a 4 foot by 4 foot grow area. (12 plants or less)
*A 600 watt* fixture will supply enough light to cover a 5 foot by 5 foot grow area. (18 plants or less)
*A 1000 watt* fixture will supply enough light to cover a 6.5 foot by 6.5 foot grow area. (30 plants or less)
In order for the heat produced by a light system not to harm the plant, a 250 watt light system should be started 18 to 30 inches above the tops of the plants, a 400 watt light system should be started 3 to 4 feet above the tops of the plants, 
A 600 watt light system should be started 4 to 5 feet above the tops of the plants, a 1000 watt light system should be started 5 to 6 feet above the tops of the plants. 
*The light should* be lowered a few inches everyday until the light is as close as it can be without harming the plant. You will have to figure out the optimal distance yourself because it will vary depending on bulb efficiency, quality of reflector, and other things. 
Whatever your light source, replace bulbs after 6 to 12 months of use. If the light is on 24 hours a day replace it after 6 months. If the light is on 18 hours a day replace it after 9 months. If the light is on 12 hours a day replace it after 12 months. 
One note about replacement bulbs, they can be divided into three categories: vertical, horizontal, universal. Vertical bulbs have to be used with fixtures in the vertical position. Horizontal bulbs have to be used with fixtures in the horizontal position. Universal bulbs can be used in a horizontal or vertical position. If you aren't sure what to buy, make sure you get a universal bulb. It will work in either type of fixture. 
*The standard ceiling* is 8 feet (96 inches) from the floor, most hydroponic systems are on a platform that is 18 to 30 inches off the floor and the plant itself will probably be 18 to 36 inches tall when fully grown. 
In most cases if your ceiling isn't more than 8 feet (96 inches) from the floor, the largest light system you should get is 400-600 watts. 400-600 watt systems are used by a majority of marijuana growers who are growing for personal consumption. If you need more light, get 250, 400, or 600 watt lights rather than 1000 watt lights. 
Experienced growers know how to limit the height of a plant by making plants grow horizontally as opposed to the natural vertical growth marijuana plants follow. The first time grower should use a 1000 watt light systems only in areas with ceiling heights of 10 feet (120 inches) or more


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