Roofing Shingle Calculator
Enter your roof footprint and pitch to estimate shingle bundles — with waste, starter course, and ridge caps included.
Runs entirely in your browser — your numbers never leave this page.
How it works
Roofers sell shingles by the "square" — 100 square feet of roof. Architectural shingles come 3 bundles to a square. The math:
Roof area = Footprint × Pitch multiplier
Bundles = (Roof area ÷ 100) × (1 + Waste) × 3
- Pitch multiplier converts flat footprint to slope area — a 6/12 pitch multiplies area by 1.30; a steep 12/12 doubles it (2.07).
- Waste: 10% for a simple gable, 15% with hips and valleys, 20% for cut-up roofs with dormers. Running short mid-job is far costlier than a spare bundle.
- Ridge caps cover the peak — one bundle covers ~33 linear feet of ridge.
- Starter strips go along eaves and rakes under the first course; buy them, don't cut field shingles for this.
- Don't forget underlayment (felt or synthetic), drip edge, and flashing — shingles are only the top layer.
Frequently asked questions
How many shingle bundles do I need?
Compute roof squares (area ÷ 100), add waste, multiply by 3 bundles per square. A 2,000 sq ft roof at 6/12 pitch is ~26 squares → ~29 with waste → 87 bundles of architectural shingles.
What is a roofing "square"?
100 square feet of roof area. It is the trade unit for shingles, felt, and roofing labor quotes.
How do I measure roof pitch?
Pitch is rise over a 12-inch run. Hold a level 12 inches out from the roof surface and measure the vertical gap — 6 inches of gap = 6/12 pitch. Or measure in the attic from a rafter.
Architectural vs 3-tab shingles?
Architectural (dimensional) shingles are thicker, last 25–30 years, and still run 3 bundles per square. 3-tab are cheaper and flatter but last ~20 years. Most pros recommend architectural.
How much waste should I add?
10% for a simple gable, 15% for hips/valleys/dormers, 20% for complex roofs. Steeper roofs waste more because cut pieces slide and every course needs trimming.
What are ridge caps?
Pre-bent shingles that cover the roof peak where the two slopes meet. One bundle covers about 33 linear feet of ridge.
Do I need starter strips?
Yes — they seal the eave edge and give the first course something to bond to. Cutting field shingles as starters wastes time and voids some warranties.
How much underlayment do I need?
One roll of 15-lb felt covers ~4 squares; synthetic underlayment covers ~10 squares per roll. Match the underlayment squares to your shingle squares.
Can I layer new shingles over old ones?
One overlay is legal in most places, but it hides deck damage, adds weight, and shortens the new roof's life. Most roofers recommend a tear-off for a full replacement.
How do valleys and dormers change the count?
Each valley, hip, and dormer adds cutting waste — step up to the 15–20% waste tier. For very cut-up roofs, measure each plane separately and add them up.