Exterior

Roofing Calculator: Squares, Bundles and Cost

Roof area, squares and shingle bundles from your footprint and pitch — plus underlayment, ridge cap and a replacement cost range.

Your measurements

Roofing squares

13.8squares

1,252 sq ft of roof plus 10% waste — 1 square = 100 sq ft

House footprint
1,120 sq ft
Actual roof area6/12 pitch multiplies the footprint by 1.118
1,252 sq ft
With waste
1,377 sq ft
Shingle bundles3 bundles per square
42
UnderlaymentSynthetic, 10 squares per roll
4 rolls
Ridge capRidge plus hips, rough allowance
46 ft
Drip edgeEaves and rakes
143 ft
Installed cost$450–$750 per square installed
$6,198 – $10,330
  • A roofing 'square' is 100 sq ft. Every quote you receive will be priced by the square, so this is the number to compare bids on.
  • The pitch multiplier is the whole point — a 40 × 28 ft house has 1,120 sq ft of footprint but 1,252 sq ft of roof at 6/12 and 1,584 sq ft at 12/12. Quoting off the footprint under-orders every time.
  • Tear-off, decking replacement and a second layer removal are all extra and are the usual source of change orders. Ask any bid to state them separately.

How this is calculated

  • Roof area is the footprint multiplied by the pitch factor √(1 + (rise/12)²) — 1.054 at 4/12, 1.118 at 6/12, 1.414 at 12/12.
  • Waste is 10% for a simple gable, 15% with hips or dormers, 20% for a complex roof — valleys and penetrations generate offcuts that cannot be reused.
  • A square is 100 sq ft and takes 3 bundles of standard shingles. Synthetic underlayment covers 10 squares per roll.
  • Installed cost ranges are typical 2025–2026 US pricing per square, including labour and standard tear-off of one layer.

Quantities are rounded up, because materials are sold in whole units and a second trip costs more than a spare box. Cost figures are typical US ranges and are not a quote — always price against your own supplier.

Frequently asked questions

How many squares is my roof?

Multiply your house footprint by the pitch factor, then divide by 100. A 40 × 28 ft house at 6/12 pitch has 1,252 sq ft of roof, which is 12.5 squares — about 14 squares once waste is included.

How many bundles of shingles per square?

Three bundles per square for standard architectural and 3-tab shingles. Heavier premium and designer shingles can run four or five bundles per square — check the wrapper.

How much does a new roof cost?

For asphalt architectural shingles, $450–$750 per square installed, so a typical 25 square roof is $11,000–$19,000. Metal and tile run two to three times that. Steep pitch, multiple existing layers and difficult access all push the figure up.

Know the quantities. Now see the room.

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