Skip to content
TrueSquare
Open menu

Roof Area Calculator

Turn a building footprint and roof pitch into sloped roof area, roofing squares and an estimated number of shingle bundles.

Formulas reviewed 13 November 2026 · See the formula

Roof Area Calculator

Footprint
ft
ft
in
Pitch
Allowances
%

≈10 % for simple gable roofs; 15 % or more for hips, valleys and dormers.

Shingles (optional)

Many asphalt shingles are packed 3 bundles per square, but check the wrapper — some products differ.

Cost estimate (optional)
USD each

Enter your local price to estimate cost. Prices vary by supplier and region.

Results

Roof area to cover (incl. waste)
1,652.9 ft²
153.56 m²
Roofing squares
16.53 squares
1 square = 100 ft² (9.29 m²)
Sloped roof area (no waste)
1,502.6 ft²139.6 m²
Footprint incl. overhangs
1,344 ft²124.86 m²
Pitch used
6/12 (26.6°)
Shingle bundles
50 bundles
  • Assumes every roof plane shares the same pitch. Measure complex roofs plane by plane.

Estimates only. Prices are your own inputs in USD; material properties vary by product and supplier.

About the roof area calculator

You can estimate roof area from the ground: measure the building, add the overhang, and multiply by the pitch multiplier. For any roof whose planes all share the same pitch — gable, hip or shed — the sloped area is the plan area times the multiplier, regardless of the roof shape.

Roofing materials in the US and Canada are sold by the square (100 ft²); elsewhere area is normally quoted in square metres. Both are shown.

How to use it

  1. Measure the outside of the walls for length and width.
  2. Enter the overhang on each side (eaves and rakes).
  3. Enter the pitch as X/12, rise and run, or degrees.
  4. Choose a waste allowance and, for shingles, the number of bundles per square printed on the wrapper.

Formula

Plan area

A_plan = (L + 2 × overhang) × (W + 2 × overhang)

Roof area

A_roof = A_plan × √(1 + (rise ÷ run)²)

Squares

squares = A_roof × (1 + waste %) ÷ 100 ft²

Bundles

bundles = ⌈ squares × bundles per square ⌉
  • The plan-area method is exact for roofs with a single pitch. For mixed pitches, dormers or complex intersections, calculate each plane separately.

Worked example: A 40 ft × 30 ft house, 12 in overhang, 6/12 pitch

  1. Plan area = 42 × 32 = 1,344 ft²
  2. Roof area = 1,344 × 1.1180 = 1,502.6 ft²
  3. +10 % waste = 1,652.9 ft² = 16.53 squares
  4. At 3 bundles per square: 49.6 → 50 bundles

Result: About 16.5 squares, or 50 bundles of shingles.

Assumptions and limitations

  • Bundles per square varies by product; many asphalt shingles are packed at 3 bundles per square but check the wrapper.
  • Starter strip, ridge caps, underlayment and flashing are not included.

Frequently asked questions

How many squares is my roof?

Divide the sloped roof area in square feet by 100. A 1,500 ft² roof is 15 squares before waste.

How much waste should I add for roofing?

Around 10 % for a simple gable roof and 15 % or more for hip roofs, valleys and dormers, where more shingles are cut.

Can I calculate roof area from the footprint?

Yes, for roofs where all planes share one pitch: multiply the footprint (including overhangs) by the pitch multiplier.

Sources and further reading

Results are estimates for planning purposes. See our disclaimer for details.