Calcs.ToolsRoofing Calculator - How Many Shingles Do I Need?
Calculate exactly how many roofing squares and shingle bundles you need for your roof replacement or new construction project. Our free roofing calculator accounts for roof pitch, eave overhang, and provides accurate material estimates to ensure you purchase the right amount of asphalt shingles, underlayment, and flashing.
How to Use the Roofing Calculator
- Measure your house: Enter the house length and width in feet. Measure from the exterior walls, not including overhangs.
- Select roof pitch: Choose the appropriate pitch ratio (rise over run) for your roof. Most residential roofs are 4/12 to 6/12 pitch.
- Set eave overhang: Select the typical overhang distance. Most homes have 1.5-2 feet of overhang.
- Review results: Get total roofing squares and shingle bundles needed, including waste factors.
Pro tip: For complex roofs with multiple pitches, dormers, or hips/valleys, divide the roof into separate sections and calculate each one individually.
Understanding Roofing Calculations
Roofing calculations are complex because they must account for roof pitch, overhangs, and the three-dimensional nature of roof surfaces. Understanding these calculations helps you make informed decisions about your roofing project.
Roofing Squares
A "square" is the standard roofing measurement equal to 100 square feet of roof surface. All roofing materials are sold by the square, and contractors estimate projects using squares.
Pitch Multiplier Effect
Roof pitch dramatically affects material requirements. A steep roof needs significantly more shingles than a flat roof of the same footprint because you're covering the sloped surface, not just the floor area.
- Flat roof (2/12): ~6% more material than floor area
- Standard roof (4/12): ~17% more material than floor area
- Steep roof (8/12): ~33% more material than floor area
- Very steep (12/12): ~50% more material than floor area
Example: A 30×40 foot house with 4/12 pitch roof requires approximately 17.5 squares of shingles, covering about 1,750 square feet of roof surface.
Waste Factors in Roofing
Roofing always involves waste from cutting shingles to fit around vents, skylights, and roof edges. Typical waste factors range from 5-15% depending on roof complexity.
Roofing Materials & Installation
Asphalt Shingles
- • Most common residential roofing
- • 3 bundles = 1 square of coverage
- • 20-30 year warranty typical
- • Cost: $80-150 per square
- • Easy DIY installation for simple roofs
Underlayment Requirements
- • 15lb felt paper standard
- • Ice/water shield in cold climates
- • Self-adhering membrane for valleys
- • Required by building codes
- • Protects against water damage
Flashing & Accessories
- • Drip edge for all roof edges
- • Step flashing for chimneys/walls
- • Valley flashing for roof valleys
- • Vent flashing for plumbing vents
- • Ridge vent for attic ventilation
Installation Tips
- • Start at bottom, work up
- • Use chalk lines for straight courses
- • Stagger seams for strength
- • Nail properly (4-6 nails per shingle)
- • Seal all penetrations
Roofing Cost Factors & Considerations
Cost Breakdown per Square
- Materials: $80-150 (shingles, underlayment, flashing)
- Labor: $75-200 (depending on roof complexity)
- Disposal: $50-100 (old roof removal)
- Permits: $50-200 (varies by location)
- Total per square: $255-650 installed
Factors Affecting Cost
- Roof pitch: Steeper roofs cost more to work on
- Roof complexity: Hips, valleys, dormers increase cost
- Accessibility: Two-story homes cost more
- Material quality: Premium shingles cost more
- Location: Urban areas have higher labor costs