🏠 Roofing Calculator
Calculate roofing materials needed
How to Use This Calculator
Enter Roof Dimensions
Input the length and width of your roof in feet. For gabled roofs, measure the length and width of the roof footprint (not the ground).
Specify Roof Pitch (Optional)
Enter the roof pitch in inches rise per 12 inches run. Common pitches: 4/12 (low), 6/12 (standard), 8/12 (moderate), 12/12 (steep). This accounts for increased surface area on sloped roofs.
Calculate Roofing Squares
Click "Calculate Roofing" to see roofing squares needed. One square equals 100 square feet. The calculator automatically adds 10% waste for cuts and overlaps.
Order Materials
Use the squares result to order shingles, underlayment, and other materials. Roofing materials are typically sold by the square. Add extra for hip roofs, valleys, and complex roof shapes.
Formula
Base Area = Length × Width
Pitch Multiplier = √(1 + (Rise/Run)²)
Roof Area = Base Area × Pitch Multiplier
Roofing Squares = Roof Area ÷ 100
Example 1: Flat Roof (40 ft × 30 ft, no pitch)
Step 1: Calculate base area: 40 × 30 = 1,200 sq ft
Step 2: No pitch multiplier: 1,200 × 1 = 1,200 sq ft
Step 3: Calculate squares: 1,200 ÷ 100 = 12 squares
Step 4: Add waste: 12 × 1.10 = 13.2 squares → 14 squares
Example 2: Pitched Roof (40 ft × 30 ft, 6/12 pitch)
Step 1: Calculate base area: 40 × 30 = 1,200 sq ft
Step 2: Calculate pitch multiplier: √(1 + (6/12)²) = √(1 + 0.25) = √1.25 = 1.118
Step 3: Calculate roof area: 1,200 × 1.118 = 1,341.6 sq ft
Step 4: Calculate squares: 1,341.6 ÷ 100 = 13.4 squares
Step 5: Add waste: 13.4 × 1.10 = 14.7 squares → 15 squares
About Roofing Calculator
The Roofing Calculator is an essential tool for contractors, roofers, homeowners, and builders who need to accurately determine how many roofing squares are required for their roofing projects. This calculator eliminates guesswork by providing precise measurements accounting for roof pitch, waste, and overlaps, helping you order the right amount of shingles, underlayment, and other roofing materials.
When to Use This Calculator
- New Roof Installation: Calculate roofing materials needed for new roof construction projects
- Roof Replacement: Determine shingles, underlayment, and materials needed for roof replacement
- Roof Repair: Estimate materials for partial roof repairs or patch work
- Budget Planning: Estimate costs by calculating roofing squares and material quantities
- Contractor Estimates: Quick reference for contractors bidding roofing projects
Why Use Our Calculator?
- ✅ Pitch Calculation: Automatically accounts for roof pitch to calculate actual surface area
- ✅ Roofing Squares: Provides results in roofing squares (standard unit for shingles)
- ✅ Waste Allowance: Automatically includes 10% extra for cuts, overlaps, and waste
- ✅ Cost Estimation: Helps budget accurately by determining exact material needs
- ✅ Time Savings: Instant calculations eliminate manual math and pitch conversions
- ✅ Professional Results: Industry-standard formulas ensure contractor-quality estimates
Common Applications
Residential Roofing: Homeowners and contractors planning new roofs or replacements use this calculator to order the correct quantity of shingles, underlayment, and accessories. Standard asphalt shingles are sold in squares (100 sq ft bundles), which this calculator helps determine accurately.
Commercial Roofing: Contractors working on commercial projects use this tool to estimate materials for flat roofs, pitched roofs, and complex roof structures, ensuring sufficient materials are on-site before starting work.
Roof Repair Work: Roofers planning repairs use this calculator to determine materials needed for partial replacements, patch work, and maintenance projects.
Tips for Best Results
- Measure Carefully: Take multiple measurements and use averages for irregular roof shapes
- Account for Pitch: Steeper roofs require more material—always enter pitch for accurate results
- Add Extra for Complex Roofs: Hip roofs, valleys, and dormers require 15-20% extra material
- Check Building Codes: Verify local requirements for underlayment, ice dams, and ventilation
- Order Bundles: Shingles come in bundles (~33 sq ft); 3 bundles = 1 square, but verify with supplier
Frequently Asked Questions
How many roofing squares do I need for a 40×30 foot roof?
For a flat 40×30 foot roof (1,200 sq ft), you'll need approximately 13-14 squares including waste. For a 6/12 pitch roof, you'll need about 15 squares due to increased surface area from the slope.
What is a roofing square?
A roofing square equals 100 square feet. It's the standard unit for selling roofing materials like shingles and underlayment. One square typically contains 3 bundles of shingles covering 100 sq ft.
How does roof pitch affect material needs?
Steeper roofs have more surface area than flat roofs of the same footprint. A 6/12 pitch increases surface area by about 12%, an 8/12 pitch by about 18%, and a 12/12 pitch by about 41%. Always enter pitch for accurate calculations.
Should I order extra roofing materials?
Yes! Always add 10-15% extra for waste, cuts around vents and chimneys, overlaps, and future repairs. For complex roofs with valleys, hips, or dormers, add 15-20% extra.
How many shingles are in a square?
One square typically contains 3 bundles of standard asphalt shingles, covering 100 sq ft. Bundle counts vary by shingle type—always verify with your supplier. Some specialty shingles may have different bundle sizes.
Can I use this for metal or tile roofs?
This calculator works for any roofing material sold by the square. For metal roofing, tiles, or other materials sold by linear feet or pieces, you'll need to convert the square footage result to the appropriate unit based on your material specifications.