How Does This Calculator Work?
The calculator adds your waste percentage to the roof area, then divides by 100 (the size of one roofing "square") and rounds up, since shingles are sold by the full square/bundle.
Roofing shingles are ordered in "squares" (100 square feet of coverage each). This calculator converts your roof area into squares needed, with a waste allowance for cuts and ridges.
Example Calculation
Gable Roof Example
A 1,700 sq ft roof, 10% waste allowance.
(1700×1.10)/100 ≈ 18.7, rounded up to 19 squares.
Tips
A 10% waste allowance is typical for simple gable roofs; use 15% or more for complex roofs with many hips, valleys, and dormers.