Multiply the width measurement by the length measurement to find the area of the ceiling. This is the square foot measurement of the ceiling and the amount of area you must cover with one coat of paint.Click to see full answer. Similarly, how do you calculate the square footage of a ceiling?Determine the length and width of the ceiling in a rectangular room by taking measurements from corner to corner. Multiply the length by the width to obtain the gross ceiling area. For example, a room 15 feet long and 10 feet wide has a gross ceiling area of 150 square feet — 15 times 10 = 150.Similarly, how do you estimate a ceiling? Divide the width of the ceiling in two to determine how many runners you need for the ceiling grid. The runners are the metal brackets that run the length of the ceiling. You divide the width of the ceiling by two because the tiles are 2 feet wide. Similarly one may ask, how do you find the square footage of a wall and ceiling? Measure the height of the walls from the floor to the ceiling. If you own a multi-storey home, measure from the floor to the ceiling of the top storey. Measure the length and width of all exterior windows and doors. [(Exterior perimeter × height) − (window and door area)] ÷ 144 = total square footage.How do I calculate square footage?If you are measuring a square or rectangle area, multiply length times width; Length x Width = Area. For other area shapes, see formulas below to calculate Area (ft2) = Square Footage.