Roofing Calculator
Estimate the surface area of a gable or hip roof from its footprint and pitch, then convert it to roofing squares and shingle bundles with waste included — plus ridge cap and drip edge lengths. Roofs with valleys, dormers, and mixed pitches need professional measurement.
- Flat footprint area
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- Pitch-adjusted roof area
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- Pitch multiplier
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- Roofing squares (exact)
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- Shingle bundles (approx.)
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- Ridge cap
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- Drip edge
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- Estimated material cost
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Bundles assume 3 per square; ridge cap ≈ 25 ft per bundle.
Common questions
What is a roofing square?
A roofing square is 100 square feet of finished roof surface. Roofers price and order materials in squares, so a 2,000 sq ft roof surface is 20 squares. Note this is roof surface area, not the footprint of the house.
How many squares is my roof?
Divide the pitch-adjusted roof area by 100. A 40 ft × 30 ft footprint is 1,200 sq ft flat; at a 6/12 pitch the actual roof surface is 1,200 × 1.118 = 1,342 sq ft, or about 13.4 squares. Add waste — typically 10% on a simple gable — before ordering.
How many bundles of shingles are in a square?
Three bundles per square is the standard for three-tab and most architectural shingles. So a 20-square roof needs about 60 bundles of field shingles, plus starter strip and ridge cap. Some premium and designer shingles are packaged 4 or 5 bundles per square — check the wrapper before you order.
How does roof pitch change the number of squares?
Pitch multiplies the flat footprint by √(1 + (rise ÷ 12)²). A 4/12 pitch adds about 5% (×1.054), 6/12 adds 12% (×1.118), 8/12 adds 20% (×1.202), and 12/12 adds 41% (×1.414). Ignoring pitch is the most common way roof estimates come in short.
How many bundles of shingles do I need for 1,000 square feet?
About 30 bundles for 1,000 sq ft of roof surface (10 squares × 3 bundles), or roughly 33 bundles once a 10% waste allowance is included. If 1,000 sq ft is the footprint rather than the roof surface, apply the pitch multiplier first.
How do I calculate shingles for a hip roof?
Choose Hip and enter the footprint and pitch. With the same pitch on all four sides, a hip roof has the same surface area as a gable on that footprint, so the squares match. The difference is about 15% waste instead of 10%, plus ridge cap along all four hips as well as the shorter ridge.
Does this work for complex roofs?
Only for a single gable or hip on a rectangular footprint. Valleys, dormers, wings, and mixed pitches add surface area and generate far more cut waste, commonly 20% or more. Have a complex roof measured professionally or from a satellite measure-up before ordering.
How this is calculated
- This models a single gable or hip roof on a rectangular footprint, with the same pitch on every plane. Valleys, dormers, wings, and mixed pitches make real roofs larger and more wasteful than this estimate.
- Starter strips, underlayment, flashing, and vents are not included. Ridge cap coverage varies by product (roughly 20–35 linear feet per bundle).
- Three bundles per square assumes standard shingles; some premium products use 4–5 bundles per square.
- The default waste is 10% for a gable and 15% for a hip, which has angled cuts along all four hips; cut-up roofs commonly need 20%.
- Any roof beyond a simple gable or hip should be measured by a professional (or from a satellite measure-up) before ordering.
- Asphalt Roofing Manufacturers Association (ARMA) — estimating guidance — Roofing square = 100 sq ft; pitch factor table matches √(1 + (rise/12)²).
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