You're ready to tackle painting your bedroom, but how do you know how much paint you need? If you're buying a custom-tinted color, you usually can't return it just because you bought too much. If you buy too little, you run the risk that the paint won't be an exact match when you buy that additional gallon. So take a few measurements and do some calculations before you go paint shopping, and the amount of paint you buy should be just right.
Measure the width and height of the first wall in the room. Multiply the two figures to calculate the wall's square footage.
Measure the rest of the walls in the same way and figure the square footage of each. If you're painting the ceiling the same color as the walls, measure the length and width of the ceiling and calculate its square footage.
Add up all the square footage numbers to get the total square footage of the area to be painted. Round up to the nearest 100. Multiply the total by 2 if you will be applying two coats of paint. So if your room has 350 square feet to paint, your final square footage will be 700.
Check the label of the paint can to see how many square feet its contents will cover. This can vary from 200 to 400 square feet, depending on the product and the texture of the wall. Divide your final square footage by this number to determine how many cans of paint you will need. For instance, if you need 700 square feet of coverage on a smooth wall and a gallon covers 400 square feet of smooth surface, you will need to buy two cans.