How to Calculate Roofing Needed
- 1). Measure the length of one rectangular section of the roof.
- 2). Measure the width of the same rectangular section of roof.
- 3). Multiply the length by the width to find the area of that section of roof.
- 4). Repeat for the remaining sections of roof, measuring every area you will be laying shingles.
- 5). Add the areas of all the sections of roof.
- 6). Divide the area by 100 square feet, as a square of shingles covers an area 10 feet by 10 feet, or 100 square feet.
- 7). Round the number up to determine the number of squares of shingles you need.
Source...