Go to How Not to Build an Addition Index! This page includes notes on calculating the number of bundles necessary for a job.

HOW MANY SHINGLES YOU WILL NEED

The quantity of materials needed for a job will be based on the surface area of the roof that is to be covered. There is a simple formula for figuring this out:

Length X Width = Area

Make sure you measure actual surface areas and not just the perimeter of your roof. When estimating, factor in cutting, slop, ridge lines, and extra for a dog house.

Three bundles of shingles make a "square". A square theoretically covers 100 square feet. I have found this rule of thumb to be accurate if you don't make too many mistakes with the utility knife.

Roofing:Tools and Materials
Shingles
Shingle Transport
Felt Paper and Tar
How Many Shingles
Safety
Shingle Surfing
Laying Shingles

How You Really Shingle a Roof!

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About the Author:
W.J. Rayment built an addition on his house, and in the course of the project learned from his many mistakes. This on-line compendium is his effort to help you learn from his experience. The advice and stories are often humorous, sometimes silly, but always informative. You can get a real paperback copy of this book by W.J. Rayment for yourself or as a gift for family or friends.