Measure each area of the roof, in feet, to determine how many shingles will be needed.
Multiply the length of each area by the width to determine the square footage.
Add the amount of square footage for each area together. This will give you the entire square footage of the roof and will allow you to estimate the number of shingles, and thus nails, needed.
Divide the entire square footage by 100 to reach the estimated amount of shingles needed.
Multiply the estimated amount of shingles by 2 to 2 1/2. The resulting figure is an estimate of the pounds of nails needed.