Roofing Shingle Calculator
Roofing is sold by the square (100 sq ft) and shingles by the bundle (3 bundles per square). Enter your roof size and pitch to get both, with waste included.
Roofing Shingle Calculator
About this roofing shingle calculator
A roofing square covers 100 square feet, and a square of standard 3-tab shingles comes as 3 bundles. (Architectural shingles vary — some need 3 to 4 bundles per square, so check your product.) This calculator starts from your roof's footprint, corrects for pitch — a steeper roof has more surface area than its footprint suggests — and adds waste for cuts around hips, valleys, and penetrations.
Measure length along the eave and width from eave to ridge on one slope, then double the width for both slopes. If your roof has dormers or complex geometry, break it into rectangles and run each through the calculator, then add the results.
The 10% waste default suits a simple gable roof. Bump it to 15% for roofs with hips, valleys, dormers, or skylights — every angle means more cut shingles in the scrap pile.
How to use
- Measure the roof length along the eave in feet.
- Measure from eave to ridge on one slope and double it for the roof width.
- Select your roof pitch — 6/12 is the most common residential pitch.
- Choose a waste allowance (15% for complex roofs) and press Calculate.
Good to know
- Assumes 3 bundles per square (standard 3-tab). Verify bundles-per-square for your shingle product.
- Does not include underlayment, ice-and-water shield, flashing, drip edge, ridge caps, or nails — budget those separately.
- Complex roofs should be measured in sections; a single rectangle will undercount.
- Roofing is skilled, dangerous work at height. This estimates materials only — get professional quotes for labor.
Frequently asked questions
How many shingles do I need for a 20x30 roof?
A 20×30 ft roof footprint is 600 sq ft; with a 6/12 pitch that is about 671 sq ft of roof surface, or 6.7 squares before waste — roughly 23 bundles once 10% waste is added. Enter your exact pitch above for your number.
What is a roofing square?
A roofing square is 100 square feet of roof coverage. Roofers quote materials and labor per square.
How many bundles of shingles per square?
Three bundles per square for standard 3-tab shingles. Architectural/dimensional shingles can require 3–4 bundles per square — check the manufacturer's spec.
How does roof pitch affect shingle quantity?
Steeper roofs have more surface area. A 12/12 pitch roof has about 41% more area than its flat footprint; a 6/12 pitch adds about 12%. The calculator applies the pitch multiplier automatically.
How much waste should I add for shingles?
10% for a simple gable roof, 15% for roofs with hips, valleys, dormers, or skylights.