How Many Square Feet in One Square Shingle?

When it comes to roofing, the term "square" refers to 100 square feet of roof area. So when you hear roofers talk about needing 30 squares of shingles, they are referring to enough shingles to cover 3,000 square feet of roof surface. But what does this translate to in terms of actual shingles? That depends on the size and dimensions of the shingles being used.

We'll look at how to measure shingle size, account for overlap, and determine how many shingles make up one square. With this knowledge, you'll be better equipped to estimate materials and budget accurately for your next roofing project.

Defining a "Square" of Shingles

First, let's clarify what constitutes one square of shingles. This is the standard roofing industry term used to estimate quantities and pricing:

• 1 square = enough shingles to cover 100 square feet of roof area
• Shingles are bundled together, with each bundle equaling one square
• So a "square" of shingles contains the number of shingle pieces needed to cover 100 square feet of roof surface

The actual number of shingle pieces in a square will vary based on size, style, and manufacturer. But one square will contain the appropriate amount to install over 100 square feet of roof.

Typical Shingle Square Size and Dimensions

Most asphalt shingles are available as either architectural or 3-tab style. 3-tab shingles are more affordable and have three cutouts creating a tabbed look. Architectural shingles have a more dimensional, layered appearance. Let's look at standard sizes for each:

• 36" long x 12" wide
• Approximately 3 square feet per shingle
• 33 pieces per bundle/square

• 36" long x 13 1/4" wide
• Approximately 3.25 square feet per shingle
• 31 pieces per bundle/square

As you can see, architectural shingles are slightly larger in width compared to 3-tabs. But overall one square contains about 100 sq ft of coverage either way. Other specialty shingles like slate or metal may come in different sizes.

Factoring in Exposure

When calculating total square footage of a shingle square, you also need to account for exposure. Exposure refers to the amount of shingle material left exposed to the elements. Shingles are intentionally installed with overlap so that only a portion is exposed.

For both 3-tab and architectural shingles, a standard exposure is 5". This means each horizontal shingle row covers 5" of the row below it. Exposure may vary from 4"-6" based on roof pitch and weather conditions in your region. But using 5" will give you an accurate base measurement.

Calculating Square Feet Within a Shingle Square

Now that we understand the size of a single shingle and standard exposure, we can calculate total coverage area. Let's break down the math using 3-tab and architectural shingles as examples:

3-Tab Shingle Square Footage

• 3-tab shingle dimensions = 36" long x 12" wide = 3 sq ft per shingle
• Standard exposure of 5" leaves 7" of the shingle exposed
• 7" exposure x 12" width = 84 sq in exposed per shingle
• 84 sq in / 144 sq in per sq ft = 0.58 sq ft exposed per shingle
• 33 shingles per bundle with 0.58 sq ft exposure each = 19.14 sq ft

So for 3-tab shingles , each 33-piece bundle covers about 19 square feet of actual roof area. In other words, you need just over 5 bundles to cover 100 square feet. This shows why it takes 33 pieces to equal one square--the overlap factors in to total up to 100 sq ft of coverage.

Architectural Shingle Square Footage

• Dimensions = 36" long x 13 1/4" wide = 3.25 sq ft per shingle
• With 5" exposure, 8 1/4" exposed x 13 1/4" wide = 109 sq in
• 109 sq in / 144 = 0.76 sq ft exposed per shingle
• 31 shingles per bundle x 0.76 sq ft each = 23.56 sq ft

For architectural shingles , each 31-piece bundle covers about 24 square feet . So you would need roughly 4 bundles to equal one square's worth of coverage. Again, the overlap is factored into the total coverage area.

Visual Representation

To help visualize how overlap impacts coverage, here is a diagram showing shingle exposure:

As shown above, each horizontal shingle row covers up a portion of the row below it. Exposure is measured based on how much of the shingle surface remains uncovered. This exposure measurement allows you to calculate total coverage within a bundle square.

Factors That Impact Shingle Square Size

While we used standard sizes and exposure measurements above, there are a few variables that can impact the actual square footage within a shingle bundle:

Manufacturer Specifications

Keep in mind exact shingle dimensions can vary slightly by manufacturer. So always check the size charts on packaging or product websites when estimating materials.

Regional Building Codes

Depending on roof pitch and climate, your local building codes may require more or less exposure. This would alter the square footage calculations. Check regional guidelines when planning your project.

Type of Shingles

Specialty shingles like slate, metal, or solar panels will have different sizes and coverage amounts. The measurements above apply specifically to asphalt 3-tab and architectural shingles. Other types would require separate calculations.

Estimating Number of Shingle Squares

Now that you understand the square footage within a shingle bundle, let's discuss how to estimate the number of squares needed for an entire roof:

Measure Roof Size

First, you'll need accurate measurements of the total roof area. Measure the dimensions of each slope and roof plane and input into a roofing calculator . This will give you the total square footage to be covered.

Divide by 100

Next, take the total roof square footage and divide by 100. This tells you how many squares are needed. For example, a 2,000 sq ft roof would require 20 squares of shingles (2,000 sq ft / 100 = 20 squares).

Add a Buffer

It's smart to add an extra 10-20% as a buffer. Complex roofs often require more materials than initial measurements. And having extras allows for mistakes, repairs, and future replacements if needed.

Budgeting Costs Based on Squares

In addition to estimating material quantities, roofing contractors also base project pricing around the number of squares. This allows you to quickly compare bids and budget installation costs. Here's what to expect: