How to Estimate How Much Paint to Buy for a Room
One of the easiest ways to give a room a makeover is to apply a fresh coat of paint. In addition to estimating the amount of paint needed to cover the walls, you also may need to estimate how much primer is needed and how much paint to buy for the trim and doors. A few simple formulas will help you get a reasonable estimate of the amount of paint and primer you need to buy for the entire room. Does this Spark an idea?
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Instructions
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Calculate the square footage of the walls to be painted by adding the lengths of all the walls, then multiplying the total by the height of the room. From this number, subtract 20 square feet for each door and about 15 square feet for each average-sized window.
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Calculate the number of gallons of wall paint you need by dividing the total square footage of the wall space by 350 (one gallon of paint will cover about 350 square feet). Use the same formula to determine how much primer to buy. If painting with a dark color, it may be necessary to apply two coats of paint. Multiply the number of gallons of paint needed by two if that is the case.
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Calculate the square footage of the ceiling by multiplying the length of the room by the width. Divide this number by 350 to calculate how many gallons of ceiling paint you need.
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Calculate the amount of door and trim paint needed by measuring the length of all of the trim in the room, including the trim around doors, windows, ceiling and any built-in units. This measurement should be in feet. Multiply this total length by 0.5 (1/2 foot) as an estimate of the average width of the trim. The resulting number is the total estimated square footage of trim.
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Add the total square footage of the doors to the square footage of the trim. Each door will require about 20 square feet of the same paint used for the trim. If you paint both sides of the door, allow 40 square feet. Divide the square footage of the doors and trim by 350 to calculate how many gallons of trim paint is needed.
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Tips & Warnings
While 350 square feet is a good general estimate of how much coverage you'll get with one gallon of paint, you should always check the label on the can of paint. Different brands and formulations may get different coverage. Also, the texture of the walls you are painting will affect how much paint is needed. A smooth wall will need less paint than a highly textured wall. Adding a tint to the primer will help get better coverage with dark paint colors.
When buying paint, err on the side of buying a bit too much rather than too little. Exact color matching will be difficult if you must go back to buy additional paint.
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- Photo Credit Rob Jenkins
