Roofing Calculator
Calculate how many roofing squares, shingle bundles, and sheets of underlayment are needed based on roof area and pitch.
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Roof Area
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Roofing Squares —
Bundles Needed —
Extended More scenarios, charts & detailed breakdown ▾
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Roofing Squares
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Bundles (3-tab) —
Bundles (arch.) —
Roof Area —
Professional Full parameters & maximum detail ▾
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Roof Quantities
Roof Area —
Roofing Squares —
Bundles (3-tab) —
Cost Breakdown
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Installation —
Underlayment —
Flashing / Misc —
Tear-off —
Total Project Cost —
Cost per Sq Ft —
How to Use This Calculator
- Enter the roof footprint length and width in feet (the flat ground dimensions, not the slope).
- Select the roof pitch (rise per 12 inches of run).
- Enter the waste percentage and bundles per square.
Formula
Roof area = Footprint area × Pitch factor
Pitch factors: 4/12→1.054, 6/12→1.118, 8/12→1.202, 12/12→1.414
Squares = Roof area ÷ 100 | Bundles = Squares × bundles/square × (1 + waste%)
Example
Example: 30 × 40 ft footprint, 6/12 pitch, 10% waste, 3 bundles/sq → Area 1,342 sq ft → 44 bundles.
Frequently Asked Questions
- One roofing square equals exactly 100 square feet of roof surface area. Shingles are sold in bundles, and typically 3 bundles of standard three-tab shingles cover one square. Architectural (dimensional) shingles are thicker and heavier, often requiring 4 bundles per square — always check the manufacturer specification on the bundle packaging. To estimate your order, calculate the roof area in square feet, divide by 100 to get squares, then multiply by the bundles-per-square figure for your chosen shingle product.
- Roof pitch increases the actual sloped surface area compared to the flat horizontal footprint. A 4/12 pitch (rises 4 inches per 12 inches of run) has a pitch multiplier of 1.054, meaning a 1,000 sq ft footprint has 1,054 sq ft of actual roof surface. A steep 12/12 pitch has a multiplier of 1.414 — 41% more surface than the footprint. This calculator applies the correct pitch factor automatically when you enter your roof pitch. Always measure the actual sloped surface or use the pitch multiplier on your footprint measurement.
- Most residential roofs in the US have a pitch between 4/12 and 6/12. A 4/12 pitch rises 4 inches vertically for every 12 inches of horizontal run, creating a moderate slope common on ranch-style homes. A 6/12 pitch is steeper and more common on colonial and two-story homes. Pitches below 2/12 are considered low-slope and typically require modified bitumen or metal roofing rather than shingles. Very steep pitches (above 12/12) are rare and significantly increase labor cost because safety equipment is required.
- Standard three-tab asphalt shingles typically use 3 bundles per square (100 sq ft). Architectural or dimensional shingles are heavier and thicker, usually requiring 4 bundles per square — verify on the bundle label. Premium designer shingles may use 5 bundles per square. Metal roofing panels are sold by linear foot, not bundles. When calculating, always check the coverage listed on the specific product you plan to buy, as coverage can vary by manufacturer even within the same product category.
- Yes — always add a waste allowance on top of your calculated roof area. For a simple gable roof, 10% waste is typical. For hip roofs with multiple valleys and hips, use 15% waste because more cuts are required at each ridge and valley. Roofs with many dormers, skylights, or complex geometry may need 20% waste. The calculator includes a configurable waste percentage in the extended tabs. Ordering too little requires a second delivery with a possible color match issue if the dye lot has changed. Keep a few extra bundles for future repairs.