Roofing Calculator
Roofing materials are measured in squares — one square covers 100 square feet. This roofing calculator converts your roof area into squares, shingle bundles, and ridge cap bundles, giving you everything you need to estimate materials for a shingle roofing project.
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Formula
Squares = ceil(Roof Area / 100 × 1.1)
Roof area in square feet divided by 100 gives roofing squares. Multiplying by 1.1 adds 10% waste. Standard shingles require 3 bundles per square. Ridge cap needs roughly 5% of total squares.
How to use the Roofing Calculator
- 1
Enter your roof area (sq ft)
Value should be in sq ft.
- 2
Read your results instantly
Results update in real time as you type.
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Measuring Roof Area
Roof area is larger than your home's footprint due to pitch and overhangs. For a quick estimate, measure your home's footprint and multiply by a pitch factor (1.0 for flat, 1.15 for 4:12 pitch, 1.30 for 6:12 pitch, 1.50 for 9:12 pitch). For accuracy, measure each roof plane directly — the rafter calculator on this site can help determine actual roof surface dimensions.
Shingle Types and Bundles
Standard three-tab shingles and most architectural shingles come 3 bundles per square. Some premium architectural shingles are heavier and come 4 bundles per square — always check the manufacturer specification. You'll also need underlayment (1 roll per 4 squares), drip edge, starter strips, and roofing nails. Don't forget to account for valleys and hips which require extra material.
Tips & Insights
Add Extra for Complex Roofs
Roofs with multiple hips, valleys, dormers, or skylights need 15–20% waste instead of 10%. Each interruption creates cuts that waste shingles.
Measure the Roof, Not the House
Your home's floor area does not equal your roof area. Pitch increases the surface area significantly. A steep 12:12 pitch roof has 41% more surface area than the footprint.
Check for Matching Batches
If buying shingles for a partial re-roof, bring an old shingle to match the color. Manufacturers change shingle colors over product generations, and even the same name can look different.
Worked Examples
Ranch Home Re-Roof
20 roofing squares with waste — 60 bundles of shingles and 1 bundle of ridge cap needed.
Two-Story Colonial
36 roofing squares — 108 bundles of shingles for the main field.
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Frequently Asked Questions
What is a roofing square?
A roofing square is 100 square feet of roof coverage. It's the standard unit for ordering shingles, underlayment, and other roofing materials.
How many bundles of shingles are in a square?
Most standard shingles require 3 bundles per square. Some premium architectural shingles require 4 bundles per square. Check the manufacturer's packaging.
How long does a shingle roof last?
Three-tab shingles typically last 20–25 years. Architectural (dimensional) shingles last 25–30 years. Premium designer shingles can last 40–50 years with proper installation and ventilation.
Do I need to remove old shingles before re-roofing?
Most building codes allow one layer of new shingles over one existing layer. Adding a third layer is generally not permitted. Tearing off old shingles (a full tear-off) gives a better final result and lets you inspect the decking.
How do I calculate roof pitch?
Pitch is measured as rise over a 12-inch run. A 6:12 pitch rises 6 inches for every 12 inches of horizontal run. Use our roof pitch calculator to find the exact pitch of your roof.
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