Q: How do I calculate the amount of roofing shingles needed for a roof?
A: Roofing material is calculated by taking measurements of each roof section (length x width) and adding them all together to calculate the area of the entire roof in square feet. Triangular sections of a roof, as with hip roofs, can be computed by multiplying the ridge length by the height of the side, then dividing by half. Add together the area of all the sides of the roof, and then add 10 to 15 percent to account for waste. Roofing shingles are sold by the “square” (100 sq. feet), so determine the number of squares of shingles needed by dividing the total area by 100.