# How do you calculate how many shingles are needed for your building project?

Professional roofing contractors typically provide estimates of materials needed for roofing, including the number of shingles needed. Simple geometric calculations can provide a rough estimate.

1. ### Calculate the square footage of the roof

Multiple the length times width for every flat surface on your roof, including dormers. Add together all the totals to get the total square footage.

2. ### Divide the square footage by 100

Shingles are sold in "squares," which are 100 square foot sections of roofing. Unless you are applying shingles directly to an already existing asphalt roof, you probably also need the same amount of underlayment. Divide the roof's total square footage by 100 to determine the number of squares of shingles needed.

3. ### Add an extra 10 percent

Add 10 percent to your total to make sure you have enough shingles for trim.

Reference:
Q&A Related to "How do you calculate how many shingles are needed..."
 1. Measure each plane of your roof, length and width. Record the length and width of each plane and then multiply these numbers together to get the square footage of each plane of http://www.ehow.com/how_4514291_calculate-shingles...
 I'm pretty sure you count the number down and the number across and find the area for every face of the roof you have. then add all of the totals together. http://wiki.answers.com/Q/How_do_you_calculate_the...