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Roofing Calculator

Calculate roof surface area, shingle bundles, and squares for gable, hip, or shed roofs based on pitch and footprint.

Construction

Roofing Calculator

Generated on April 25, 2026

Roof diagram (top-down)

Ridgelength = 40 ftwidth = 30 ftpitch angle ≈ 26.6°
Materials needed
Roof surface area1341.6 ft²
With 10% waste1475.8 ft²
Squares (US)14.76
Shingle bundles45
1 US "square" = 100 sq ft = 3 standard asphalt-shingle bundles. Hip roofs add ~5% wastage at the diagonal cuts.

Step-by-step calculation

Formula

Roof area = footprint × pitch factor (e.g. 6/12 pitch = ×1.118). Pitch factor = √(1 + (rise/run)²). Order = area × (1 + waste%).

  1. 1Building footprint: 40 × 30 = 1200.00 ft².
  2. 2Pitch 6/12 → factor ×1.118 (angle = 26.6°).
  3. 3Roof surface area = 1200.00 × 1.118 = 1341.60 ft².
  4. 4With 10% waste: 1341.60 × 1.10 = 1475.76 ft².
  5. 5≈ 14.76 squares × 3 bundles = 45 bundles of asphalt shingles.

?What is the Roofing Calculator?

The Roofing Calculator estimates roof surface area, the number of shingle bundles, and the US-conventional 'squares' (1 square = 100 sq ft) needed for a re-roofing or new-build job. Supports the three most common roof shapes: gable (two slopes meeting at a ridge), hip (four slopes meeting at a central ridge — common in cyclone-prone regions and modern Pakistani houses), and shed (single slope, common in extensions and modern flat-look architecture). Pitch is entered in the standard X/12 notation (rise per 12 units of horizontal run) used by every roofing supplier worldwide. Includes adjustable waste percentage (typical 10% for gable, 15% for hip due to diagonal cuts).

The Formula

Roof surface area = footprint × pitch factor. Pitch factor = √(1 + (rise/run)²). Bundles = ceil(area_sq_ft × waste% ÷ 33.33).

The pitch factor accounts for the actual sloped surface vs the flat footprint underneath. A 6/12 pitch (very common roof angle, ~26.6°) has a pitch factor of √(1 + (6/12)²) = √1.25 ≈ 1.118 — meaning the actual roof surface is about 12% larger than the floor plan area beneath it. Steeper pitches add even more area: 12/12 (45°) has factor √2 ≈ 1.414. US asphalt shingles come in bundles that cover ~33.33 sq ft each (3 bundles per square = 100 sq ft).

Practical Examples

1

30×40 ft house with 6/12 gable roof: footprint 1,200 sq ft × 1.118 = 1,341 sq ft of roof. With 10% waste: 1,476 sq ft = 14.76 squares = 45 bundles.

2

Hip roofs need ~15% extra material vs gable for the diagonal cuts on the four hip seams.

3

Pakistani / South Asian flat / mono-pitch (1/12 to 3/12) roofs use less shingle area but lose drainage advantage.

4

Steep alpine roofs (12/12 or 14/12) shed snow and ice but require more shingles — 41% more than the floor plan.

5

A standard asphalt-shingle bundle weighs ~65 lbs and covers about 33 sq ft. Plan your delivery vehicle accordingly.

Frequently Asked Questions

A US trade unit equal to 100 sq ft of roofing surface — easier to think about than huge sq-ft numbers. A standard asphalt-shingle bundle covers 1/3 of a square (33.3 sq ft), so 3 bundles = 1 square. Quotes and orders are usually expressed in squares.

Popular Conversions

Jump to a ready-made conversion — useful for quick reference and sharing:

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