Project Parameters
Ground-level footprint of the roofed structure.
10% for simple gable roofs; 15-20% for hips, dormers, and valleys.
Instant Estimate
Roofing Squares (100 sq ft)
1 square covers 100 square feet of roof surface.
Shingle Bundles (3 per square)
Standard architectural asphalt shingles come 3 bundles per square.
Underlayment Rolls (400 sq ft/roll)
Synthetic or 30-lb felt underlayment.
Estimated Ridge & Hip Cap Length
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Guide
How to calculate roofing materials
Roof surface area is always greater than the house's flat footprint due to the roof pitch slope and eave overhangs. Roofers order materials in 'squares' (100 sq ft) and buy shingles in 3-bundle bundles.
Determine Flat Footprint & Overhang
Measure exterior ground dimensions of the roofed area and add 1 to 2 feet for the eave and rake overhang.
Apply Pitch Multiplier
Multiply the flat area by the pitch slope factor (e.g. 1.118 for a 6:12 pitch, or 1.202 for an 8:12 pitch).
Add Valleys & Waste Allowance
Add 10% for basic gable roofs or 15% for complex hips, valleys, and skylights.
Convert to Squares and Bundles
Divide total square footage by 100 to get squares. Multiply squares by 3 to get shingle bundle count.
Mathematics
Formulas used
True Roof Surface Area
Footprint Area × Overhang Factor (1.08) × Pitch MultiplierAccounts for the triangular hypotenuse slope of the rafters.
Roofing Squares
Total Surface Sq Ft with Waste / 1001 square = 100 sq ft of installed roof surface.
Bundles of Shingles
Roofing Squares × 3Asphalt shingles are packaged in 3 bundles per square (each weighing ~65-80 lbs).
Answers & FAQ
Frequently asked questions
How many bundles of shingles are in a square?▼
For standard 3-tab and architectural asphalt shingles, there are 3 bundles in one square (100 sq ft). Very heavy luxury or designer shingles may come 4 or 5 bundles per square.
How do I find my roof pitch?▼
Roof pitch represents how many inches the roof rises vertically for every 12 inches of horizontal run. A 6:12 pitch rises 6 inches over a 12-inch horizontal distance.
How much does a new roof cost in 2026?▼
Materials alone range from $110 to $160 per square for architectural shingles ($2,500 to $4,500 for a 2,000 sq ft home). Full professional tear-off and replacement installed typically runs $8,500 to $18,000.
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