To estimate roofing materials, start by finding the total square footage of the roof and divide the number by 100 to determine the number of squares on the roof. Since 3 packs of shingles are needed to cover a square, plan to buy 3 packs for each square. Then, add 10% to the number to account for waste. To estimate how many shingles you'll need, first calculate the total square footage of the roof surface.
To do this, measure the length and width of each plane on the roof, including the dormers. Then, multiply the length by the width to get the square footage of each plane. Finally, calculate the total square footage of your roof by simply adding up the square footage of each of the planes.