Calculator guide
Estimate roof area and material quantity from plan dimensions and roof pitch.
Formula or method
Sloped area = plan area × pitch factor; a common factor is √(1+(rise/run)²) for one roof surface.
How to use this calculator
- Enter building plan length and width.
- Enter pitch or select the supported roof form.
- Review area and material estimate, then add the supplier's waste and packaging factors.
Worked example
A 30×40 ft plan is 1,200 ft². At a 6:12 pitch, factor √(1+.5²)=1.118, so one overall sloped area is about 1,342 ft² before waste.
Understanding the result
Roofing is sold in squares (100 ft²); flashing, valleys, hips, eaves, and waste can materially change the order.
Limitations and assumptions
- Assumes simplified geometry and may not model multiple planes, overhangs, or dormers.
- A roof measurement is not a substitute for a safe professional inspection.
Frequently asked questions
What is a roofing square?
One roofing square equals 100 square feet of roof area.
How much waste is needed?
It depends on roof complexity and material; ask the installer or supplier.
Can I measure from the ground?
Ground estimates can miss geometry; use safe methods and professional verification.
Sources
Educational information only; verify important decisions with a qualified professional.