How to Determine How Many Bundles of Shingles to Use on a Roof

Your roof may be nearing the end of its useful life if it's more than 10 years old, especially if harsh weather conditions have damaged your shingles. Although the expense of the job leads many homeowners to put it off for as long as possible, deferring replacement may cause you more headaches in the long run. You can save thousands of dollars in labor costs by doing the work yourself. Or, if installing a new roof is beyond your capabilities, you can still save by acting as your own contractor. One of your first tasks in this role is to figure out how many bundles of shingles you’ll need to complete the job.

Pen
Paper
Tape measure
Ladder
Calculator

Instructions

- 1
  Draw a rough diagram of your roof. Include each plane, whether it's shaped like a rectangle or triangle.
- 2
  Measure the dimensions of each plane. Note them on your diagram.
- 3
  Find the area of each rectangular plane in square feet. Multiply the length by the height of each one. For example, for a rectangular plane that's 20 feet long and 15 feet high, multiply 20 by 15 to arrive at an area of 300 square feet.
- 4
  Find the area of each triangular plane in square feet by multiplying the base by the height and dividing by two. The height of the triangle is the distance from the base to the peak, as measured with a straight vertical line. For example, for a triangular plane that's 10 feet wide along the base and 20 feet high at its peak, as measured in a line extending straight up from the base, multiply 10 by 20 to arrive at 200, then divide by 2. The area is 100 square feet.
- 5
  Compute the total square footage of the roof by adding together the areas of each rectangular and each triangular plane.
- 6
  Divide the total square footage by 100 square feet to find how many squares – a “square” is 100 square feet -- of roofing you'll need. For example, if your roof is 1,000 square feet, divide 1,000 by 100 to arrive at 10 squares.
- 7
  Multiply the number of squares by three, as most shingle manufacturers package shingles in 1/3-square bundles of 33.3 square feet, so you need three bundles for each square. Thirty bundles of shingles cover a 10-square roof.
- 8
  Add 10 percent to the number of bundles you need to make up for waste. The waste material consists of the shingles you trim along the edges of the roof. For a 30-bundle roofing job, 10 percent is three bundles. The total number of bundles required for the job is 33.

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