Deciding to improve the color of a room in your home with a fresh coat of paint is only half the battle. The next hurdle is figuring the amount of paint you need to complete the project. Typically, a gallon of paint will cover 350 square feet of space when applied correctly. A few measurements of your room and some simple calculations will provide you with an accurate figure.
Measure the width, height and length of the room. Write down each measurement.
Measure the height of the baseboard. Write down the measurement.
Multiply the width by the height of the room. Double this figure to attain the square footage of both short walls. For example, if the width is 10 feet and the height is 8 feet, one wall is 80 square feet and the two walls equal 160 square feet.
Multiply the length by the height of the room. Double this figure for the square footage of both long walls.
Add the amounts of square footage of the width by the height and the length by the height of the room for total square feet.
Measure the width and height of each door and window in the room. Write down the measurements.
Multiply the width by the height of the doorways and windows to figure their square feet.
Measure any archways in the same way.
Subtract the door, window and archway square footage measurements from the total square foot area of the room. For example, if the total for the room is 480 square feet and the square foot area of the doors, windows and archways is 212, you'll end up with 268 square feet to paint.
Purchase 1 gallon of paint to cover this example room, because it is less than 350 square feet.