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Roofing Cost Calculator

A roofing cost calculator tells you how much a reroof will cost. It takes the house footprint and the roof pitch, and returns the roof area in squares, the bundles of shingles, and the installed cost. Type your footprint below and pick the pitch. Everything runs in your browser, with no signup.

Updated for 2026

Your roof

Enter the footprint and pick the pitch. Results update instantly.
ft
ft
%
$/ square
Installed roof cost
$0
Roof area
0 ft²
Squares (with waste)
0
Bundles
0
Cost per ft²
$0
Slope factor applied
1.0

How roof pitch changes the area

The slope factor turns the flat footprint into the actual sloped roof area. For a 40 by 30 ft footprint with 10% waste. Tap a row to load that pitch.

PitchSlope factorRoof areaSquares

How the roofing estimate is calculated

Roofing is sold by the square, which is 100 square feet. The roof area is the footprint times the slope factor for the pitch. Divide by 100 for squares, add waste, then price it:

Squares = Footprint × Slope factor ÷ 100 × (1 + Waste)

The slope factor is the square root of one plus the pitch squared, so a 6 in 12 roof is about 1.118. Asphalt shingles come three bundles to a square. This assumes a simple roof over the whole footprint; hips, valleys, and dormers add area and waste, so treat the result as a planning estimate.

Worked example (Stand: 2026)
  • Footprint40 ft × 30 ft
  • Plan area (40 × 30)1,200 ft²
  • Pitch6 in 12 (factor 1.118)
  • Roof area (1,200 × 1.118)1,342 ft²
  • Squares (1,342 ÷ 100)13.4
  • With 10% waste (13.42 × 1.10)14.76 squares
  • Bundles (14.76 × 3, rounded up)45
  • Cost (14.76 × $450)$6,641

Frequently asked questions

How many squares of shingles do I need?
Multiply the footprint by the slope factor for the roof area, then divide by 100 and add waste. The calculator above does this and gives the bundles and an installed cost.
What is a roofing square?
100 square feet of roof. Roofing is sold and priced by the square, and asphalt shingles come three bundles to a square.
How much does a new roof cost?
About 350 to 550 dollars per square installed for asphalt in 2026, so a typical roof often lands between 6,000 and 12,000 dollars. Steep or complex roofs and premium materials cost more.
Why does pitch matter?
A steeper roof has more surface than its footprint. The slope factor, from about 1.03 at 2 in 12 to 1.41 at 12 in 12, scales the footprint up to the real roof area.
Does this calculator store my numbers?
No. Everything is calculated in your browser. Nothing you enter is sent to a server or saved.

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