Method
How to calculate roofing squares to purchase
The slope factor adjusts plan area for pitch. Roofing squares represent 100 square feet before the entered waste allowance.
FORMULASlope area = plan area × √(1 + (rise ÷ 12)²)
Worked example
Roofing-material calculator example
A 6-in-12 pitch uses a slope factor of about 1.118, increasing surface area above the horizontal plan.
Change one assumption at a time to see what drives the result. The output is an estimate, not a quote, forecast or recommendation.
FAQ
Roofing-material calculator FAQ
What is a roofing square?
One roofing square covers 100 square feet of roof surface.
Does this include overhangs?
Only if the entered length and run include them.
Can this replace a roof measurement?
No. Valleys, dormers, hips and irregular sections should be measured separately by a qualified professional.