Roof Calculator
Estimate roofing materials by calculating the roof area from length, width, and pitch. Determine the number of shingle bundles and roofing squares needed for your project.
About this Calculator
Estimate roofing materials by calculating the roof area from length, width, and pitch. Determine the number of shingle bundles and roofing squares needed for your project.
Formula & Calculations
Formula
Roof Area = Length × Width × (1 + (Pitch Rise / Pitch Run)²)^(1/2); Squares = Roof Area / 100; Bundles = Squares × 3Where:
- L=Length of the roof in feet
- W=Width of the roof in feet
- Pitch=Roof pitch expressed as rise over run (e.g., 4:12 means 4 inches of rise per 12 inches of run)
- Area=Total roof surface area in square feet (accounting for pitch)
- Squares=Roofing squares (1 square = 100 sq ft)
Assumptions
- Assumes a simple gable roof with two equal rectangular planes.
- One bundle of shingles covers approximately 33.3 square feet (3 bundles per roofing square).
- Does not account for waste factor; consider adding 10-15% for cuts and overlaps.
- Pitch factor is calculated as √(1 + (rise/run)²).
Calculation Examples
Example 1
Pitch factor = √(1 + (4/12)²) ≈ 1.054. Roof area = 40 × 30 × 1.054 × 2 planes? No, 40 × 30 × 1.054 = 1,264.9 sq ft for one side. Two sides = 2,529.8 sq ft total. Squares = 25.3, bundles ≈ 76.
Example 2
Pitch factor = √(1 + (6/12)²) = √1.25 ≈ 1.118. Roof area = 50 × 25 × 1.118 = 1,397.5 sq ft per plane.
Frequently Asked Questions
How many bundles of shingles are in a roofing square?
Three bundles of standard asphalt shingles typically cover one roofing square (100 square feet). Always check the manufacturer's specifications, as coverage can vary.
Should I include a waste factor?
Yes, it's standard practice to add 10-15% extra material for waste due to cutting, ridge caps, and starter strips. Multiply the calculated bundles by 1.10 to 1.15 for your final order.