Roof Shingle Calculator

🏠 Roof Shingle Calculator

Roof Length (ft)

Roof Width (ft, one side)

Roof Pitch

Number of Roof Sides/Planes

📊 Roofing Materials Needed

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Understanding Roofing Squares

Roofing is measured in squares — one square equals 100 square feet. Most shingle bundles cover about 33 sq ft, so you need 3 bundles per square. Always add 10–15% for waste, hips, ridges, and valleys.

Starter strip shingles: 1 bundle per 100 linear feet of eaves.
Ridge cap: typically 1 bundle per 35 linear feet of ridge.
Underlayment rolls: 1 roll covers approximately 400 sq ft.

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How to Use This Calculator

Measure your roof's length and width from the ground — use the house footprint dimensions as a starting point.
Select your roof pitch: low (nearly flat), standard (most common), steep, or very steep. Pitch affects the actual roof surface area significantly.
Select the number of roof planes: 2 for a standard gable, 4 for a hip roof, or more for complex designs.
The calculator outputs roof area in square feet and squares, plus shingle bundles, underlayment rolls, and nails needed.
Always order 10–15% extra for waste — valleys, ridges, and starter courses consume additional material.

The Formula Explained

Sloped Area = L × W × Sides × Pitch Factor | Squares = Area ÷ 100 | Bundles = Squares × 3 × 1.12

Roofing is measured in "squares" — one square equals 100 square feet of roof surface. Most standard 3-tab and architectural shingles come in bundles that cover about 33 sq ft, meaning you need 3 bundles per square. The pitch factor accounts for the additional surface area created by slope: a 12/12 pitch (45° angle) has roughly 41% more surface area than the same footprint measured flat. The calculator applies a 12% waste buffer on top of the base bundle count.

Material Buying Guide

A complete roofing project requires more than just shingles. Here's what to budget and buy:

Architectural Shingles: The standard choice for most homes. Cost $100–$150 per square installed. Dimensional texture looks better than 3-tab and carries 25–30 year warranties. Most popular brands: Owens Corning, GAF, CertainTeed.
Synthetic Underlayment: Preferred over felt paper — lighter, stronger, and doesn't absorb moisture if rain hits before shingles are laid. One roll covers 10 squares (1,000 sq ft).
Ice and Water Shield: Self-adhering membrane required at eaves, valleys, and penetrations in most building codes. Typically covers the first 3 feet of eave plus all valleys. Budget 1–2 squares per valley.
Ridge Cap Shingles: Specialized shingles for the peak — sold separately and calculated by ridge linear footage. One bundle covers about 35 linear feet of ridge.
Roofing Nails: Use 1-3/4" galvanized coil nails. Budget roughly 0.75 lbs per square for standard 3-tab; 1 lb per square for architectural shingles.
Drip Edge: Metal flashing along eaves and rakes — sold in 10-foot sections. Measure your eave and rake perimeter to calculate sections needed.

Frequently Asked Questions

How many bundles of shingles do I need per square?

Standard architectural shingles use 3 bundles per square (one square = 100 sq ft of roof area). Some premium shingles with larger exposure may use 4 bundles per square — check the manufacturer specification on the bundle label.

Can I install new shingles over old ones?

Most building codes allow one layer of new shingles over existing — this saves the cost of tear-off. However, re-roofing over old shingles hides the decking condition, adds weight, and voids most shingle warranties. A full tear-off is almost always the better long-term investment.

What is roof pitch and how do I measure it?

Roof pitch is expressed as rise-over-run: a 6/12 pitch rises 6 inches for every 12 inches of horizontal run. To measure it, hold a level horizontally against the roof, measure 12 inches out from where it touches, then measure straight down to the roof surface — that measurement is your pitch numerator.

How long does a roof replacement take?

Most residential roofs (1,500–2,500 sq ft) are completed in 1–2 days by a professional crew. Larger or more complex roofs with dormers, multiple penetrations, or steep pitches may take 3–4 days. Tear-off adds half a day to most projects.

How much does a new roof cost?

Architectural shingles installed cost $4–$8 per square foot, meaning a 1,500 sq ft ranch costs $6,000–$12,000 and a 2,500 sq ft colonial runs $10,000–$20,000. Metal roofing costs $10–$20/sq ft. Premium slate or tile runs $20–$50/sq ft installed.

🏗️ Pro Tip: Add 10% waste factor for simple gable roofs, 15% for hip roofs, and up to 20% for complex roofs with dormers, valleys, or skylights. Order starter strips and ridge cap shingles separately — they're not included in standard square calculations. Synthetic underlayment costs more than felt but protects the deck if installation spans multiple days of weather exposure.