Free homeowner tool
Roof size calculator
How big is your roof, in square feet and in roofing squares? Enter your footprint, overhang and pitch. It takes a minute, and you don't need a ladder.
Your roof, for planning
Enter your footprint to see the roof area and the number of squares.
Rather we measure it?
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How the calculator works
- Step 1
Footprint plus overhang
We add the overhang to every side of your footprint. That is the roof's outline seen from above — the plan area.
- Step 2
Allow for the slope
A sloped roof has more surface than its outline. The slope factor is √(1 + (pitch ÷ 12)²): about 1.05 at 4 in 12, 1.12 at 6 in 12 and 1.20 at 8 in 12. Gable and hip roofs at the same pitch come out the same.
- Step 3
Divide by 100
Roofers count roofs in squares. One square is 100 square feet of roof surface, so a 2,500 sq ft roof is 25 squares.
- Step 4
Add a waste allowance
Material gets cut at hips, valleys, rakes and edges. We show a typical planning allowance for your roof style — more cuts, more allowance.
Wondering whether you need a new roof at all? Check how much life is left in your roof, or see our roof repair page.
Roof size questions
- What is a roofing square?
- A square is 100 square feet of roof surface. Roofers measure, order material and write scopes in squares, so a roof with 2,000 square feet of surface is a 20-square roof.
- Why is my roof bigger than my home's square footage?
- Three reasons. The roof covers the garage and covered porches, which are not in the living area. It overhangs the walls on every side. And a sloped roof has more surface than the flat outline beneath it — the steeper the pitch, the bigger the difference. On a two-story home it works the other way: the roof only covers the ground-floor footprint, not both floors.
- How do I find my roof pitch without going on the roof?
- Look at your permit papers or plans, a previous roof or home inspection report, or ask a roofer — at a free estimate we measure it. Please don't climb up to measure it yourself. If you aren't sure, the calculator can show a range for 4 to 6 in 12.
- How much waste should I allow for?
- As a typical planning allowance: around 10% for a simple gable roof, around 15% for a hip roof, and 20% or more for a complex roof with valleys, dormers or several wings. Low-slope roofs usually need less. The real figure depends on the roof and the material.
- Is this accurate enough for a quote?
- No — it is for planning. Real roofs have porches at different pitches, dormers, skylights, parapet walls and other details a footprint can't show. At the free estimate we measure the actual roof and put it in a written scope.
- Does this work for tile, metal and flat roofs?
- Yes. The roof's surface area is the same whatever covers it, so the area and squares apply to shingle, tile, metal and flat roofs. What changes is the material and how it is detailed at the edges — on a flat roof with parapet walls, for example, the membrane also runs up the walls.
Get the roof measured for free
Tell us about the house. A roofer measures the real roof and gives you a flat rate price in writing.