Roofing Calculator
Estimate roofing squares and shingle bundles from building dimensions and pitch.
e.g. 6 for a 6/12 pitch — check the Roof Pitch Calculator if you need to measure it first.
Roofing squares needed
15 squares
- Actual roof area (pitch-adjusted)
- 1,341.64 sq ft
- Shingle bundles (est.)
- 45 bundles
How we calculate this
A sloped roof has more surface area than the building's flat footprint — the steeper the pitch, the bigger the difference. Roof area = footprint area × pitch multiplier, where the multiplier is √(1 + (rise/12)²). Roofing is then sold in "squares" (100 sq ft), with 3-tab and architectural shingles typically packaged 3 bundles per square.
Example
Measuring tips
Measure the building's length and width at the eaves (the flat footprint, not the sloped surface). If you don't already know your roof pitch, use the Roof Pitch Calculator first — a level and tape measure is all you need.
Common mistakes
- Using the flat footprint area directly instead of the pitch-adjusted roof area, which undercounts material on anything steeper than a low-slope roof.
- Forgetting that hips, valleys, and dormers add complexity (and waste) beyond a simple rectangular roof.
- Not accounting for starter strips and ridge cap shingles, which use additional material beyond the field squares.
Frequently asked questions
How many shingles do I need for 1,500 sq ft of roof?
Roughly 15 squares before waste, which at 3 bundles per square is about 45 bundles — add 10% waste for cuts around edges, valleys, and penetrations.
What is a roofing "square"?
A square is 100 square feet of roof surface — the standard unit roofing materials are bought and sold in.
Related calculators
Estimates are provided for planning purposes. Actual material requirements may vary based on supplier specifications, compaction, site conditions, installation method, waste, and local code.