Plan Your Project: The Ultimate Roofing Estimator
Replacing a roof is one of the most expensive home maintenance projects you will undertake. The biggest cost variable? Material waste. If you underestimate, your crew stands idle waiting for a delivery. If you overestimate, you are left with hundreds of dollars in unreturnable shingles. Our Advanced Roofing Calculator solves this by using the geometry of your home—including the pitch (steepness) and overhangs—to tell you exactly how many "Squares" and bundles you need to order.
Understanding the Lingo: What is a "Square"?
In the roofing industry, nobody talks in "square feet." They talk in Squares.
- 1 Square = 100 Square Feet (a 10ft x 10ft area).
- 3 Bundles = 1 Square. Most standard architectural shingles come in packages that cover 33.3 sq ft. So, you need 3 bundles to cover one square.
The "Pitch Multiplier" Effect
A common mistake DIYers make is measuring the floor of the attic (e.g., 40ft x 25ft = 1,000 sq ft) and buying 1,000 sq ft of shingles. This is wrong. Because a roof is angled, the surface area is actually larger than the footprint of the house.
The steeper the roof, the more shingles you need. Our calculator automatically applies the correct Pitch Multiplier based on your selection (e.g., a 12/12 pitch roof has 41% more surface area than a flat roof!).
Waste Factors: Gable vs. Hip vs. Complex
You never buy exactly the amount of roof area you measured. You need extra for cutting around vents, valleys, and starter rows. This is called the Waste Factor:
- Simple Gable (5-10% Waste): A standard "A-frame" roof. Very little cutting is required.
- Hip Roof (10-15% Waste): A roof that slopes down on all four sides. This requires cutting shingles diagonally at every corner, creating significant waste.
- Complex (15-20% Waste): Roofs with multiple dormers, valleys, and chimneys require the most extra material.
Frequently Asked Questions
How do I know my roof pitch?
Pitch is measured by "Rise over Run." A 4/12 pitch means the roof rises 4 inches for every 12 inches of horizontal length. Most standard suburban homes are between 4/12 (walkable) and 6/12. If it looks too steep to walk on safely, it is likely 8/12 or higher.
What is an Overhang?
This is the part of the roof that extends past your exterior walls to protect the siding from rain. A standard overhang is 12 to 24 inches. While it seems small, on a large house, the overhangs alone can add 1 to 2 "Squares" of material to the job.
Does this calculator include the ridge cap?
This tool calculates the field shingles. You generally need to buy specialized Ridge Cap Shingles separately for the very peak of the roof. A rule of thumb is that one bundle of linear ridge caps covers 35 linear feet of ridge.