Calculate the measurements of the room you want to paint
Find and note down the height and width of the first wall in the room. After that, multiply the two readings to find the wall’s square footage. Calculate the other walls in this same manner and find out the square footage of each and every section that you want to paint. If you are painting the exact colour on the walls and ceilings, measure the width and length of the ceiling and find out its square footage as well.
Find the total square footage of the area to be painted
Measure and add up all the numbers to find the total square footage of the room that you wish to paint. Then round the measurements up to the closest 100 and multiply the amount by 2 if you will be painting two coats of paint. If you have to paint 3 coats, then multiply the total by 3. For example, if the room has 250 square feet of area to be painted, your final square footage will be 500 if you are applying two coats of paint.
Check the contents of paint
Read the paint label to find out how many square feet it can paint. This differs from 200 to 400 square feet, mostly depending on the design of the wall. Divide the final square footage by this particular number to know how many cans are required for the paint job.