How To Calculate How Many Squares Your Roof Is: A Complete Guide For Homeowners

Estimating your roof size in squares is crucial for budgeting roofing projects, buying materials, and communicating with contractors. A “square” is a unique roofing measurement used in the U.S., equating to 100 square feet. This article breaks down how to accurately determine how many squares your roof is, explains why this metric matters, and provides easy methods, tools, and practical examples for American homeowners.

What Is A Roofing Square?

In U.S. roofing terminology, a “square” represents a 10-foot by 10-foot area—or 100 square feet. This measurement standardizes roofing material estimates, simplifying orders and bids. Contractors nearly always use squares on estimates, contracts, and invoices. Understanding it helps homeowners make apples-to-apples comparisons when reviewing professional quotes.

Reasons To Know How Many Squares Your Roof Is

• Get Accurate Estimates: Contractors quote roofing jobs by square, impacting your costs.
• Order Materials Efficiently: Shingles, underlayment, and other supplies are packaged by the square, reducing waste and overages.
• Insurance Claims: Payouts are based on your roof’s square footage in case of storm or hail damage.
• DIY Roofing Projects: You need to know the total squares to plan and budget for a self-managed reroof.

How To Calculate Your Roof In Squares: Step-By-Step

Step 1: Measure The Ground Footprint Of Your Home

Start by measuring the length and width of your house at ground level. For example, if you have a rectangular house that is 40 feet long and 30 feet wide, your ground footprint is 1,200 square feet.

Formula: Length × Width = Ground Square Footage

Step 2: Adjust For Roof Pitch (Slope)

Your actual roof surface is larger than the ground footprint due to the pitch (or slope). The steeper the roof, the more surface area it covers. Pitch is expressed as the number of inches the roof rises for every 12 inches it runs horizontally (e.g., a 6:12 pitch rises 6 inches per foot).

Roof Pitch	Pitch Multiplier
Flat (0:12)	1.00
4:12	1.06
6:12	1.12
8:12	1.20
10:12	1.30
12:12	1.41

Formula: Ground Square Footage × Pitch Multiplier = Total Roof Surface (sq. ft.)

For the example above, if the roof has a 6:12 pitch:
1,200 sq. ft. × 1.12 = 1,344 sq. ft.

Step 3: Divide By 100 To Determine Squares

The final step is to divide the total roof surface by 100. Each “square” equals 100 sq. ft.

Formula: Total Roof Surface (sq. ft.) ÷ 100 = Number of Squares

Continuing our example: 1,344 ÷ 100 = 13.44 squares. Round up to the nearest half or whole square since materials are packaged per square.

Roof Shape And Features: Adjustments For Common Roof Types

Many homes are not simple rectangles. Complex shapes, dormers, valleys, hips, and protrusions require additional measurement and calculation.

Common Roof Types

• Gable Roof: Two sloping sides, easy to measure. Multiply length × width of each slope, add together.
• Hip Roof: All sides slope downward. Break into rectangles and triangles; measure each section separately.
• Gambrel & Mansard: Multiple slopes on each side. Measure and sum each area’s square footage.
• Flat Roof: Equal to ground footprint.

How To Measure Irregular Roofs

1. Break the roof into geometric shapes (rectangles, triangles, trapezoids).
2. Measure and calculate each area.
3. Add total square footage from all sections.
4. Apply the pitch multiplier to the sum.
5. Divide by 100 to get the final number of squares.

Where To Find Your Roof Pitch And Dimensions

Accurate calculations require knowing your roof’s pitch and footprint. Here’s how to find them:

• Building Plans Or Blueprints: Check original documentation for measurements and pitch.
• Visual Measurement: Use a tape measure or laser device for length and width at ground level.
• Smartphone Apps: Apps like RoofSnap or iRoofing can help estimate pitch and dimensions using photos.
• Pitch Gauge Tool: Place a pitch gauge or level on the roof. For DIYers, a 12-inch level and tape measure can estimate rise per 12 inches of run.
• Online Measurement Tools: Some services like EagleView or Hover analyze satellite imagery or digital photos to generate professional roof reports, including pitch and square count.

Using Online Calculators Or Aerial Roof Measurement Services

For complex or high roofs, consider digital solutions. Several companies and websites specialize in calculating roofing squares remotely:

• Google Earth: Use the ruler tool to measure roof dimensions from above.
• EagleView Technologies: Professional aerial-based reports, widely used by contractors and insurers.
• DIY Calculator Websites: Enter roof length, width, and pitch to get a quick estimate of squares.

Tip: Online services may charge a fee for detailed reports but ensure safer, more accurate measurements for steep or complex roofs.

How Contractors Calculate Squares When Quoting A Project

Professional roofers may climb onto your roof or use satellite imagery. They measure every section, account for pitch, and add extra for waste:

• Starter Strips, Ridges, And Valleys: These require additional material and labor, adding small percentages to the basic square total.
• Cut Waste: Material must be trimmed around features; contractors typically add 10%-15% for waste, especially on complicated roofs.
• Overhangs And Eaves: These can increase surface area beyond the main footprint, so ensure these areas are included.

What About Shingles: How Many Bundles Per Square?

Most asphalt shingles come three bundles per square, but this varies by shingle type and manufacturer. For 13.5 squares of roof, you’ll need:

13.5 squares × 3 bundles = 40.5 bundles (round up to 41 or 42 for waste and cuts).

Always check manufacturer packaging, as some specialized or heavier-duty shingles may require 4 or more bundles per square.

Accounting For Waste, Overhangs, And Accessories

• Waste Factor: Add 10%-15% for waste on simple roofs, up to 20% for complex roofs with many valleys, hips, or cuts.
• Underlayment: Roll widths vary; calculate total square footage to know how many rolls are required.
• Drip Edge, Ridge Cap, Flashing: Measure the length of eaves, ridges, and valleys for extra materials.
• Ventilation And Skylights: Subtract these areas from the total roof square footage, but not from the material order due to practical waste.

Common Roofing Material Coverage Table

Material	Coverage Per Bundle	Bundles Per Square
3-Tab Asphalt Shingles	33.3 sq. ft.	3
Architectural Shingles	28-33 sq. ft.	3-4
Metal Roofing Panels	Vary by width/length	Order per exact sq. ft.
Clay/Concrete Tiles	Varies; measured by square	Order per exact sq. ft.

Roofing Square Calculation Example: Step-By-Step

Let’s walk through a realistic scenario:

1. Measure House: 50 ft × 28 ft (rectangle) = 1,400 sq. ft.
2. Roof Pitch: 7:12 (multiplier = 1.16). 1,400 × 1.16 = 1,624 sq. ft.
3. Total Squares: 1,624 ÷ 100 = 16.24 squares (round to 17 for materials ordering).
4. Add 10% Waste: 17 × 1.1 = 18.7 squares (round to 19 squares).
5. Shingle Bundles: 19 × 3 = 57 bundles required.

This process allows you to estimate project costs and material needs with high confidence.

FAQs: Roof Squares And Measurements

• Is a “square” always 100 square feet? Yes, in U.S. roofing terminology, one square equals precisely 100 sq. ft.
• Do contractors always measure the same way? Professional standards are similar, but methods may differ for complicated roofs or with aerial technologies.
• Can I just use the house blueprint? Blueprints give a good estimate, but be sure to add for roof pitch and features.

Tips For Accurate Self-Measurement Vs. Hiring A Professional

• Use a sturdy ladder and proper safety equipment if climbing up to take hands-on measurements.
• If nervous about heights or have a steep/complex roof, consider hiring a pro or using aerial measurement services.
• When in doubt, order slightly more material than calculated, as returns are easier than running short mid-project.

Key Search Keywords To Use When Researching Roof Squares

• How do I calculate roof squares?
• What is a roofing square?
• Roofing material calculator
• Roof square footage estimator
• How many squares is my roof?
• Roof measurement by satellite

Common Pitfalls When Counting Roof Squares

• Ignoring roof overhangs and protrusions
• Forgetting to add waste for hip/valley cuts
• Relying solely on ground measurements without adjusting for slope
• Ordering the minimum material without rounding up
• Assuming all shingles cover the same area per bundle

Awareness of these mistakes helps avoid costly surprises and material shortages.

Summary Table: How To Calculate How Many Squares Your Roof Is

Step	Action	Example
1	Measure home footprint (L × W)	40 × 30 = 1200 sq. ft.
2	Determine roof pitch & multiplier	6:12 pitch = 1.12
3	Calculate roof square footage	1200 × 1.12 = 1344 sq. ft.
4	Divide by 100 for squares	1344 ÷ 100 = 13.44 squares
5	Add for waste (10-15%)	13.44 × 1.10 = 14.78; round up
6	Estimate bundles (per square)	15 squares × 3 = 45 bundles

Final Takeaway

Knowing exactly how many squares your roof is transforms project budgeting, increases transparency with contractors, and ensures you’re never surprised by extra material costs. Whether using traditional measurement, pitch calculations, or digital tools, this guide empowers any homeowner to estimate roof squares with confidence for repairs, replacements, or new builds.