You need to know the overall length and width of each side of your roof. Be sure to measure all areas that you need to replace.

Since I am in the process of replacing the roof on my home, I will give you an example of how I figured mine.

My roof is 53' x 26' on the front and back. 53' x 26' = 1378 square feet for each side of the house for a total of 2756 square feet. So I will need 28 squares + 10% for starter course and ridge tabs. So I will need 31 squares of shingles. (note a square of shingles is 100 square feet)

Felt is much the same way in that felt covers a 3' wide strip and comes in different length rolls. I would also recommend that you use a heavy felt (thicker).

Good Luck on your roof...

Since I am in the process of replacing the roof on my home, I will give you an example of how I figured mine.

My roof is 53' x 26' on the front and back. 53' x 26' = 1378 square feet for each side of the house for a total of 2756 square feet. So I will need 28 squares + 10% for starter course and ridge tabs. So I will need 31 squares of shingles. (note a square of shingles is 100 square feet)

Felt is much the same way in that felt covers a 3' wide strip and comes in different length rolls. I would also recommend that you use a heavy felt (thicker).

Good Luck on your roof...