To conclude the example if your total roofing area is 17 300 square feet your waste allowance would be 17 300 x 1 1 730 square feet.
How to figure out square footage of a roof.
If your roof is flat or has no more than a 3 in 12 pitch you can calculate its total square footage by simply multiplying the length by the width.
Calculate square footage for a roof by measuring and by performing some basic math equations.
To calculate the size of the roof you need to measure the size of the roof as if it were flat account for roof pitch calculate square footage and finally determine how many squares of material are required for the roof the calculator above can handle all of this simply enter the length width and pitch and it will determine the size of the roof in squares.
Steep roofs measure your house at ground level then add in the roof s overhang for greater accuracy.
1square of roofing covers 100 square feet of roof a bundle is 1 3 of a square.
Multiply the square footage of your roof by 1 to get the 10 percent waste allowance.
Get the square footage of roof and divide it by 100 and it will give the number of squares you need and for every decimal number over 3 buy a bundle to achieve the amount of material.
The total amount of roofing material you need is 17 300 1 730 19 030 square feet.
In cases where a roof has a complex shape such as in the image to the right measuring the dimensions and areas of each part of the roof to calculate total area will result in a more accurate measurement of area.