Roof Shingles Calculator
Find out how many squares and bundles of shingles you need for your roof, adjusted for pitch and waste.
- Roofing squares15 squares
- Bundles of shingles45 bundles
- Actual roof area1,341.64 sq ft
- Pitch factor×1.12
How to use
- Enter the roof footprint (length × width of the house) in feet.
- Select the roof pitch (rise over run, e.g. 6/12 is a moderate slope).
- Set a waste allowance and read the squares and bundles to buy.
About this calculator
Roofing is measured in squares: one square = 100 sq ft of roof surface. This calculator multiplies the flat footprint by a pitch factor to get the actual sloped surface area, then adds a waste allowance for hip cuts, ridge caps and starter strips. Standard 3-tab or architectural shingles pack 3 bundles per square; some premium shingles use 4. Always add at least 10% waste — 15% for complex roofs with many valleys and hips.
🧮 How it's calculated
- 1Step 1 — Flat footprint: Footprint = Length × Width
- 2Step 2 — Pitch factor (slope correction): e.g. 4/12 pitch → ×1.054, 6/12 → ×1.118, 8/12 → ×1.202, 12/12 → ×1.414
- 3Step 3 — Actual roof area: Roof area = Footprint × Pitch factor
- 4Step 4 — Add waste: Area with waste = Roof area × (1 + Waste% ÷ 100)
- 5Step 5 — Squares: Squares = ⌈Area with waste ÷ 100⌉
- 6Step 6 — Bundles: Bundles = Squares × 3 (standard 3-bundle shingles)
Roof area = Footprint × Pitch factor; Squares = ceil( Roof area × (1+Waste%) / 100 ); Bundles = Squares × 3.
Frequently asked questions
What is a roofing square?+
One roofing square equals 100 square feet of roof surface area. It is the standard unit roofers use to price and order materials.
How many bundles of shingles are in a square?+
Most standard 3-tab and architectural shingles come 3 bundles per square. Some heavier premium shingles require 4 bundles per square — check the package.
How much waste should I add for shingles?+
10% is the minimum for a simple gable roof. Add 15% for roofs with hips, valleys, dormers or skylights due to extra cuts.