Painting the interior of a room requires calculating the square footage of the surface that will be covered. If you have the height and width of the interior of the room you can calculate the coverage area with a simple length times width formula. Add up the total square footage from each wall (and ceiling if you plan to paint it) and then measure all of the areas that won't be painted. Subtract
. these from the total square footage; this gives the total paintable area. A single gallon of paint will cover about 400 square feet of a flat surface or about 250 square feet of a textured one. This is for one coat. If you would rather skip all of the manual calculations, you can try one of the several online calculators available on the internet.You can use these automatic paint calculators to figure how much paint you will need to paint the interior of any size building. As long as you have the rudimentary measurements of your interior space the calculator will figure out exactly how much paint you will need to cover the surface once. Keep in mind that these calculators only figure the amount if the paint is perfectly spread, so you will need to purchase a bit more than is called for in case of spills or unexpected material absorption. For instance, a room with 8 foot walls, that is 12'x12', with one 36 inch window and one 32 inch door with 3 inch trim, will use 1.17 gallons of paint for the walls, 0.48 for the ceiling and 0.11 gallons for trim. Purchasing three gallons of paint would be fine for two coats using these measurements.If you use both methods of calculation, take an average of the two to determine the optimal amount of paint to purchase. More reference links: www.easy2diy.com/cm/easy/diy_ht_calc_index.asp?page_id=35720769 http://www.painting-ideas-techniques.com/calculatesquarefoot.html
