Roofing Calculator
Calculate roofing materials, shingles, and costs based on roof dimensions and pitch.
A roofing calculator estimates the number of shingle squares and bundles needed based on your building footprint, roof pitch, and waste allowance.
Examples
40x30 ft building with 6/12 pitch
Frequently Asked Questions
What is a roofing square?
How much waste should I plan for?
Quick Tips
- •Always round up when ordering materials -- running short is more expensive than having extra.
- •Measure your roof from the ground using the building footprint and pitch multiplier rather than climbing on the roof.
- •Order all shingles from the same production lot to avoid color variation between bundles.
A roofing calculator estimates the number of shingle squares and bundles needed based on your building footprint, roof pitch, and waste allowance.
How to Use This Calculator
Enter the building footprint dimensions, select the roof pitch, and set a waste percentage. The calculator determines the actual roof area (accounting for pitch), the number of roofing squares, and the bundles of shingles needed.
Understanding the Formula
Roof Area = Footprint Area x Pitch Multiplier. Squares = Total Area / 100. Bundles = Squares x 3 (standard 3-tab shingles). The pitch multiplier accounts for the additional surface area created by the slope.
Examples
40x30 ft building with 6/12 pitch
Flat area: 1,200 sq ft. Pitch multiplier: 1.118. Roof area: 1,341.6 sq ft. With 10% waste: 1,475.8 sq ft = 14.76 squares = 45 bundles.
Frequently Asked Questions
What is a roofing square?
A roofing square is a unit of measurement equal to 100 square feet of roof area. It is the standard unit used when ordering roofing materials.
How much waste should I plan for?
A standard gable roof typically needs 10% waste. Hip roofs or complex roofs with many valleys and dormers may need 15-20%. Very simple shed roofs may need only 5%.
Assumptions & Limitations
- Add 5-10% extra material for waste and cuts.
- Assumes a simple gable roof shape; hip roofs, dormers, and valleys require additional material beyond the waste factor.
- Bundle count is based on standard 3-tab shingles (3 bundles per square); architectural shingles may require more.