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Roofing Calculator

Estimate roofing squares, shingle bundles, and costs.

Last updated: June 13, 2026

Calculator

Roof Length

feet

Roof Width

feet

Roof Pitch

Waste Factor

Results

Roofing Squares12.9

1 square = 100 sq ft

Shingle Bundles39

3 bundles per square

Total Roof Area1288 sq ft

Includes 15% waste

Estimated Cost$4508-$7084

$350-$550 per square installed

How to Use This Calculator

1Enter the roof length in feet.
2Enter the roof width (rafter length) in feet.
3Enter the roof pitch (rise per 12 inches of run).
4View squares, bundles, underlayment, ridge cap, and waste estimate.

Formula Explanation

Roof area accounts for the slope by applying a pitch multiplier to the flat footprint area. Materials are then calculated in roofing squares (100 sq ft each).

Roof Area = Length × Width × Pitch Factor Squares = Area ÷ 100 Bundles = Squares × 3

Variables:

LengthRoof length along the ridge

WidthRafter length (eave to ridge)

Pitch FactorMultiplier based on roof slope (e.g., 6/12 = 1.118)

Worked Examples

40×25 ft roof, 6/12 pitch

1. Flat area = 40 × 25 = 1,000 sq ft
2. Pitch factor for 6/12 = 1.118
3. Actual area = 1,000 × 1.118 = 1,118 sq ft
4. Squares = 11.18, Bundles = 34

Result: 11.2 squares / 34 bundles (+ 10% waste)

Why Use This Calculator

Accounts for roof pitch in area calculation.
Converts to industry-standard squares and bundle counts.
Includes underlayment and ridge cap estimates.
Helps you verify contractor quotes.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

Tips & Best Practices

Most roofs have two or more sections — calculate each separately and add.
Standard shingles: 3 bundles per square. Architectural may vary.
Add 10-15% waste for a simple roof, 15-20% for complex roofs with valleys and dormers.
Always install ice and water shield in valleys and along eaves in cold climates.

Common Mistakes to Avoid

❌ Measuring the flat footprint and ignoring roof pitch.

✅ A steeper roof has more surface area. Always apply the pitch multiplier — a 12/12 pitch adds 41% more area.

❌ Ordering exactly the calculated amount.

✅ Always add 10-15% for waste from cuts, starter strips, and hip/ridge caps.

Frequently Asked Questions

How many bundles of shingles do I need?

Calculate your roof area (including pitch factor), divide by 100 to get squares, then multiply by 3 for standard three-tab shingles. Add 10-15% for waste.

What is a roofing square?

A roofing square is 100 square feet of roof area. It is the standard unit for ordering roofing materials. A typical home has 20-35 squares.

How long do asphalt shingles last?

Three-tab shingles last 15-20 years. Architectural (dimensional) shingles last 25-30 years. Premium architectural can last 30-50 years. Climate, ventilation, and installation quality all affect lifespan.

336 × 280 Large Rectangle

300 × 250 Medium Rectangle

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Disclaimer: This calculator is provided for informational and educational purposes only. Results are estimates and should not be used as a substitute for professional advice. RediCalc.com makes no guarantees regarding the accuracy, completeness, or suitability of any calculations. Always consult a qualified professional before making financial, health, construction, or other important decisions.

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