How to Calculate Roofing Bundles

An accurate calculation for your roofing materials ensures you don't run out or end up with more expensive bundles than you need. Shingle quantities are often described in terms of squares. A square of shingles covers 100 square feet on your roof. Because shingles are heavy, the square is broken down into bundles. Most squares are broken down into three or four bundles of shingles. If you choose a heavier shingle, it might take more bundles to make up a square. Knowing how many bundles make up a square for your specific shingles is key to the calculation.

Tape measure

Instructions

- 1
  Measure the length and width of the two main rectangular surfaces of the roof. Multiply those two numbers together to determine the roof area that needs to be covered with the shingles.
- 2
  Measure the length and width of additional areas on the roof, such as dormers or a separate area of the roof. Multiply those numbers to get that area. Add the area you calculated for all of the separate roofing areas to determine the total number of square feet needed.
- 3
  Divide your total roof area by 100 since each square has 100 square feet of shingles in it. This tells you how many squares you need total.
- 4
  Read the shingle product information to determine how many bundles make up a square. In most cases, that number is three. Multiply the number of squares you calculated by the number of bundles in a square. For example, if you need 10 squares of shingles and each square has three bundles in it, multiply 10 by three to get a total of 30 bundles.
- 5
  Add in additional bundles to your calculations to account for the starter row, any shingles you have to cut and the cap pieces for the roof. The number of additional bundles needed depends on the size of the roof and how many peaks and valleys you have on the roof.

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