Roofing Shingle & Material Calculator
Flat (0/12)
Low Slope (2/12)
Standard (4/12)
Moderate (6/12)
Steep (8/12)
Very Steep (10/12)
Extreme (12/12)
How to Calculate Roofing Materials
Calculating the amount of shingles needed for a roofing project involves more than just measuring the footprint of your home. You must account for the slope (pitch) of the roof and include a waste factor for cuts, hips, and valleys.
Understanding Roofing Terminology
- Square: In the roofing industry, a "square" is a unit of area equal to 100 square feet.
- Bundle: Shingles are typically sold in bundles. For standard 3-tab or architectural shingles, there are usually 3 bundles per square.
- Pitch Multiplier: Because a roof is angled, the actual surface area is greater than the flat ground area. A 4/12 pitch means the roof rises 4 inches for every 12 inches of horizontal run.
The Calculation Formula
To find the total number of bundles required manually, follow these steps:
- Calculate Base Area: Length × Width
- Adjust for Pitch: Base Area × Pitch Multiplier
- Add Waste: Adjusted Area × (1 + Waste Percentage)
- Convert to Squares: Total Area / 100
- Convert to Bundles: Squares × Bundles per Square
Realistic Example:
A rectangular house measuring 40ft by 25ft has a base area of 1,000 sq. ft. With a standard 4/12 pitch (1.054 multiplier), the actual roof area is 1,054 sq. ft. Adding a 10% waste factor brings it to 1,159 sq. ft. This equals 11.59 squares. At 3 bundles per square, you would need to purchase 35 bundles.
A rectangular house measuring 40ft by 25ft has a base area of 1,000 sq. ft. With a standard 4/12 pitch (1.054 multiplier), the actual roof area is 1,054 sq. ft. Adding a 10% waste factor brings it to 1,159 sq. ft. This equals 11.59 squares. At 3 bundles per square, you would need to purchase 35 bundles.
Recommended Waste Factors
A standard rectangular roof usually requires a 10% waste factor. However, if your roof has many valleys, dormers, or hips, you should increase the waste factor to 15% or even 20% to ensure you don't run out of material mid-job.
Estimation Summary
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