There are 29 shingles in a standard bundle of three-tab roofing. Each shingle is 12 inches by 36 inches. It takes three bundles to make a square, which in roofing is 100 square feet.
When using roofing materials that are heavier than normal, the manufacturer bundles fewer shingles in a package to maintain a product that is easy to handle. With heavier materials, a square might consist of four or five bundles each, with fewer shingles than the normal bundle.
Owens Corning offers a metric square of shingles. Each shingle is 13 1/4 inches by 39 3/4 inches, and the square covers 99.98 square feet using 65 shingles. With the metric square, each bundle contains 22 shingles.