Use this Roofing Shingle Calculator to estimate roof area, roofing squares, shingle bundles, and optional material cost from the roof footprint and pitch.

Roofing Shingle Calculation Method

Footprint area = roof length × roof width × number of sections

For a roof pitch expressed as rise per 12 inches of run:

Pitch multiplier = √(rise² + 12²) ÷ 12

Sloped roof area = footprint area × pitch multiplier

Shingle area needed = sloped roof area × (1 + waste percentage ÷ 100)

Roofing squares = shingle area needed ÷ 100

Bundles needed = shingle area needed ÷ coverage per bundle

Round the bundle quantity up to the next whole bundle.

When a bundle price is entered:

Estimated cost = bundles needed × price per bundle

Example

Suppose a roof footprint is 40 ft by 30 ft with a 6/12 pitch, 10% waste allowance, and bundle coverage of 33.3 ft².

Footprint area = 40 × 30 = 1,200 ft²

Pitch multiplier = √(6² + 12²) ÷ 12 ≈ 1.118

Sloped roof area = 1,200 × 1.118 = 1,341.6 ft²

Shingle area needed = 1,341.6 × 1.10 = 1,475.76 ft²

Roofing squares = 1,475.76 ÷ 100 = 14.76 squares

Bundles needed = 1,475.76 ÷ 33.3 = 44.32

Round up to approximately 45 bundles.

Important Notes

• Use the actual coverage printed on the shingle bundle or product specification.
• Measure overhangs and separate roof sections when they are not included in the entered footprint.
• Roofs with different pitches should be calculated as separate sections.
• Hips, valleys, dormers, chimneys, skylights and complex layouts may require additional waste.
• The estimate does not include starter shingles, ridge caps, underlayment, flashing, drip edge, nails, ventilation products, delivery or labour.

Sources

• IKO — Shingle Bundles, Roofing Squares and Pitch Factors
• Owens Corning — Estimating Roofing Squares and Shingle Bundles