Roofing Shingles Calculator
Calculate how many roofing shingles you need in squares and bundles. Enter roof area and pitch.
How to use this tool
- Enter the roof's horizontal length and width (one side) in feet.
- Set the pitch multiplier (6/12 pitch is about 1.12).
- Add a waste allowance of 10–15% for cuts around hips and valleys.
- The result shows total roof area, squares, and bundles to purchase.
Estimate roofing material before your next re-roof or new construction project.
Formula
Sloped roof area (ft²) = Length × Width × 2 × Pitch multiplier
Area with waste (ft²) = Sloped area × (1 + Waste% ÷ 100)
Roofing squares = Area with waste ÷ 100
Bundles needed = ⌈Squares × 3⌉
How it works
Roofing area is calculated by taking the footprint of one roof side (length × width), doubling it for both sides of a gable roof, and multiplying by a pitch multiplier that accounts for the increased surface area on a sloped roof (e.g., 1.12 for a 5:12 pitch). A waste factor is applied before converting to roofing squares (1 square = 100 ft²). Standard three-tab shingles require approximately 3 bundles per square, so the calculator rounds up to the nearest whole bundle. Hip roofs and complex cut lines may need a higher waste percentage.
Worked example
Worked example
- Roof: 40 ft long × 20 ft wide (one side), pitch multiplier 1.12, 10% waste.
- Sloped area = 40 × 20 × 2 × 1.12 = 1792 ft².
- Area with waste = 1792 × 1.10 = 1971.2 ft².
- Squares = 1971.2 ÷ 100 = 19.712 squares.
- Bundles = ⌈19.712 × 3⌉ = ⌈59.136⌉ = 60 bundles.
Roof area = 1792 ft²; roofing squares = 19.712; bundles needed = 60.
Key terms
- Roofing square
- A unit of roofing area equal to 100 square feet; the standard quantity used for ordering shingles.
- Bundle
- A packaged quantity of shingles; typically three bundles cover one roofing square for standard three-tab shingles.
- Pitch multiplier
- A factor greater than 1.0 that converts horizontal (plan) roof area to actual sloped surface area based on the roof's rise-to-run ratio.
- Roof pitch
- The ratio of vertical rise to horizontal run (e.g., 5:12 means 5 inches of rise per 12 inches of run).
- Waste allowance
- Extra material ordered to cover cuts at eaves, ridges, hips, and valleys; typically 10–15% for simple gable roofs.
Frequently asked questions
- What is a roofing square?
- A roofing square equals 100 square feet of roof surface. Standard shingles come in bundles, and 3 bundles cover one square.
- How many bundles of shingles per square?
- Most standard 3-tab or architectural shingles require 3 bundles per square (100 ft²). Heavy-weight shingles may require 4 bundles per square.