Roofing Calculator
Calculate how many shingle bundles, underlayment rolls, and roofing materials you need. Accounts for roof pitch, sections, and waste factor.
Roof Dimensions
Roof Pitch
Roofing Material
Your Results Will Appear Here
Enter your roof dimensions and options, then click “Calculate” to see how many shingles and materials you need.
Top-Rated Roofing Materials
Hand-picked products to help you get the best results on your project.
GAF
GAF Timberline HDZ Architectural Shingles
- ✓Lifetime warranty
- ✓130 MPH wind rating
- ✓LayerLock technology
GAF
GAF FeltBuster Synthetic Underlayment, 10 sq
- ✓Anti-slip surface
- ✓UV resistant 6 months
- ✓Lightweight
Owens Corning
Owens Corning Duration Architectural Shingles
- ✓130 MPH wind warranty
- ✓SureNail technology
- ✓Algae resistant
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How to Use This Roofing Calculator
Step 1: Measure Roof
Measure the length and width of each roof section. For a simple gable roof, measure one side and use 2 sections.
Step 2: Select Pitch
Choose your roof pitch from flat to very steep. Higher pitch means more surface area. If unsure, 6:12 (medium) is the most common in the US.
Step 3: Choose Material
Select asphalt shingles, architectural shingles, or metal roofing. Each has different costs and bundle requirements.
Step 4: Add Options
Include ridge vent caps if replacing the ridge. Set the number of roof sections based on your roof shape (2 for gable, 4 for hip).
Step 5: Get Results
Click Calculate to see bundles, underlayment, ridge caps, nails, drip edge, and estimated cost for your complete roofing project.
Understanding Roof Pitch
Pitch Multiplier Table
| Pitch | Multiplier | Angle | Notes |
|---|---|---|---|
| Flat (0:12) | 1.00× | 0° | Commercial, requires special membrane |
| Low (3:12) | 1.03× | 14° | Minimum for shingles |
| Medium (6:12) | 1.12× | 27° | Most common residential |
| Steep (9:12) | 1.25× | 37° | Needs extra nails, walkable with care |
| Very Steep (12:12) | 1.41× | 45° | Requires scaffolding, specialty work |
Why Pitch Matters
Roof pitch directly affects material quantity and cost. A 12:12 pitch roof has 41% more surface area than its footprint. This means 41% more shingles, underlayment, and labor. Steeper roofs also require additional safety equipment and take longer to install.
Pro Tips for Roofing Projects
Never Roof in Rain or Below 40°F
Shingle adhesive strips need warmth (40°F+) to properly seal. Rain creates slip hazards and can damage exposed decking. Schedule your project for dry weather with moderate temperatures.
Start from Bottom Edge, Work Up and Overlap
Begin at the eave (bottom edge) and work upward. Each row overlaps the one below it, with the exposure line creating a water-shedding cascade. This is fundamental to a watertight roof.
Use 4 Nails per Shingle Minimum, 6 in High-Wind Areas
Building codes require 4 nails per standard shingle. In high-wind zones (coastal areas, open plains), use 6 nails per shingle and consider using 6-nail patterns throughout for added security.
Replace Flashing Around Vents and Chimneys
Old flashing is the most common source of roof leaks. When replacing shingles, always install new step flashing, counter flashing, and boot flashing around all penetrations.
Check Local Codes for Underlayment Requirements
Many areas now require synthetic underlayment instead of felt paper. Some regions also require ice and water shield membrane in the first 3 feet from the eave. Check your local building department before starting.
Frequently Asked Questions
A 1,000 sq ft roof equals 10 roofing squares. At 3 bundles per square plus 10% waste, you’ll need approximately 33 bundles. Our calculator also factors in roof pitch—steeper roofs have more actual surface area than the footprint suggests.
A roofing square is a unit of measurement equal to 100 square feet of roof area. Shingles are typically sold in bundles, with 3 bundles covering 1 square. When contractors give quotes "per square," they mean per 100 sq ft of roof.
Basic 3-tab asphalt shingles last 20–30 years. Architectural (dimensional) shingles last 30–50 years. Metal roofing can last 50–75 years. Actual lifespan depends on climate, ventilation, installation quality, and maintenance.
Most building codes allow up to 2 layers of asphalt shingles. However, tearing off the old layer is recommended—it lets you inspect the decking for damage, install new underlayment, and ensures proper adhesion. Check your local building codes first.
Spring and fall offer the best conditions—moderate temperatures between 45°F and 85°F. Shingles need warm temperatures to properly seal. Avoid roofing in extreme heat (shingles become too pliable), freezing temperatures, or rain.
Roof pitch is expressed as rise over run. Place a level horizontally and measure 12 inches out, then measure the vertical distance from the level to the roof surface. A 6-inch rise over 12-inch run = 6:12 pitch. Higher pitch means more actual roof area per square foot of footprint.