Roof Area Calculator
Find measured roof-section area. For sloped roofs, measure the surface directly or apply a pitch factor before ordering materials.
Free area calculator
Roof Area Calculator
Roof Area Calculator: Calculate a roof section area from measured dimensions. For pitched roofs, measure the actual roof surface or
Known Area
Room Dimensions
Multiple Rooms
Room (Feet + Inches)
ft
in
ft
in
Rectangle (Feet + Inches)
ft
in
ft
in
Wall & Window Dimensions
Cathedral Wall Dimensions
Square Dimensions
Rectangle Dimensions
Rectangle Border
Circle Dimensions
Circle Border (Annulus)
Annulus Dimensions
Triangle (3 Sides)
Triangle (Base & Height)
Trapezoid
Regular Polygon
Area + Depth (Volume)
Material Waste FactorOPTIONAL
%
Estimate Material CostOPTIONAL
Calculation Results
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How It Works
1
Select Shape
Choose the shape that matches your space.
2
Enter Dimensions
Enter measurements in any unit. Add quantity, waste factor, and material price if you need them.
3
Get Results
See area in ft², in², yd², m², and acres, plus a cost estimate when you enter a price.
Frequently Asked Questions
How do I calculate the square footage of a roof?
On a simple gable roof, measure base length and width, then multiply by a slope factor: 1.054 for 4/12 pitch, 1.118 for 6/12, 1.202 for 8/12. Or measure the roof surface directly if you can reach it safely.
What is a "roofing square" and how does it relate to square feet?
One roofing square is 100 sq ft. Shingles and underlayment are sold by the square. Divide roof area by 100 for squares needed. Add 10 to 15% for ridges, valleys, and cuts.
How do I measure roof area from the ground?
Measure the building footprint (length × width) and multiply by a pitch factor for your slope. Satellite tools and roof measurement apps help too. Complex roofs with dormers need each section measured separately.
What waste factor should I use for roofing?
Use 10% for simple gable roofs. Use 15% for hip roofs, dormers, or valleys. Use 15 to 20% for complex roofs with skylights and penetrations. Steep roofs waste more because cuts are harder.
How do I calculate ceiling area vs. roof area?
Ceiling area is flat: room length × width below. Roof area includes slope, so it is larger. A vaulted or cathedral ceiling matches roof area for that section. Flat ceilings match floor area.