How to Calculate the Amount of Shingles for a Roof
- 1). Using the tape measure, calculate the square footage of the flat parts of the roof (length times width equals area).
- 2). Divide the area by 100. This is the number of squares on your roof.
- 3). Multiply this number by three. There are three bundles per square.
- 4). Add an additional 10 to 15 percent to account for eaves, rakes, ridge caps and waste. If your roof has gables, you probably want to add 15 percent.
Source...