How to Calculate Area for Shingles
You calculate area for shingles by measuring a roof's square footage. However, to buy shingles you also need to determine the number of bundles because shingles usually come priced per bundle. Luckily, you can use very simple formulas to make these calculations.

Calculate the area for shingles of a basic gable roof that has two rectangular panels that measure 44 feet in length and 16 feet in width.

Determine the area by using the formula Length X Width since the roof is rectangular in shape. Use the length and width given in Step 1 and substitute into the formula to get 44 feet X 16 feet = 704 square feet.

Multiply 704 square feet by 2 since there are 2 rectangular panels. So the total square footage of this roof is 2 x 704 square feet = 1408 square feet.

Divide 1408 square feet by 32 square feet to find the number of bundles needed for this project. The number of bundles needed is 44. Note that you use 32 square feet because each bundle of shingle covers approximately 32 square feet (see Resources).

Add more bundles to account for waste, starter strip and caps (see Resources). The calculation of waste factors usually depends on the complexity of the shape of the roof.

Calculate the area of more complicated roofs by using other formulas (see Resources).
Things You Will Need
 Tape measure
 Calculator
Tip
 There are three ways to calculate bundles (see Resources).