What Is a Square in Roofing? 100 Sq Ft Explained

A square in roofing is a unit of measurement equal to 100 square feet of roof surface — the same as a 10-foot by 10-foot area. It is the standard way roofers measure a roof, order materials, and price a job, and it describes the roof area itself, not the floor space or square footage of your house. At Dom Roofing & Restoration, a GAF Master Elite contractor based in Sugar Hill, GA, we measure every roof across Gwinnett County and North Atlanta in squares, so this guide explains exactly what that number means for your home and your budget.

We wrote this because "square" is the single most confusing word homeowners hit on a roofing quote. Once you understand it, every estimate you read — ours or anyone else's — starts to make sense.

How big is a roofing square?

A roofing square is 100 square feet of roof surface, which you can picture as a 10 ft x 10 ft patch of roof. The key word is roof surface — not the floor space inside your home and not the footprint of the building. Because your roof is angled, its actual surface area is always larger than the ground it covers, so a 2,000-square-foot house almost never has exactly 2,000 square feet of roof. This is why we never estimate from the home's square footage; we measure the roof planes directly. In short, the square is the ruler, and your roof is what gets measured with it.

How many square feet are in a roofing square?

There are exactly 100 square feet in one roofing square. To convert between the two, the math is simple:

• Square feet to squares: divide total roof area by 100. (2,400 sq ft ÷ 100 = 24 squares.)
• Squares to square feet: multiply squares by 100. (18 squares × 100 = 1,800 sq ft.)

This is why you'll sometimes see roofing cost quoted "per square" and sometimes "per square foot" — they're the same job, just divided differently. That simple division is the foundation of every roofing estimate, which is why getting the roof measurement right matters more than any other number on your quote.

How many bundles are in a roofing square?

There are 3 bundles of asphalt shingles in one roofing square, and this holds true for both architectural (dimensional) and standard 3-tab shingles. Heavier products need more bundles because each bundle weighs more and covers less area. One bundle of GAF Timberline HDZ — the shingle we install most often across North Atlanta — covers about 33.3 square feet, so three bundles add up to roughly 100 square feet, exactly one square. (Coverage for premium and shake products varies by manufacturer.)

What else goes into one roofing square?

A square measures more than just shingles — it sets the quantity for every layer of the system. For one finished square you typically need:

• ~320 roofing nails (about 4 nails per shingle at standard exposure).
• Underlayment: synthetic underlayment covers about 10 squares per roll, while older #15 felt covers roughly 4 squares per roll.
• Starter strip, ridge cap, flashing, and ventilation, all calculated off the same square count.

Why your roof has more squares than your house's footprint

Your roof has more square footage — and more squares — than your home's footprint because of pitch (steepness). The steeper the roof, the more material it takes to cover the same ground area. We apply a pitch multiplier to convert footprint into true roof area:

This is why two homes with identical floor plans can need very different amounts of roofing if one has a steeper roof. On top of pitch, we add a waste factor: about 10% for a simple gable roof and 15% or more for complex roofs with hips, valleys, and dormers. Learn more in our pitched roof guide.

How we actually measure and quote a roof in Gwinnett & North Atlanta

Here is how our team turns a roof into a real number. First, we measure the footprint and identify the pitch, then apply the pitch multiplier to get the true roof area. We divide that by 100 to get squares, then add the waste/overage factor because cut shingles and starter courses always create some scrap.

A quick worked example for a typical home in Suwanee, Buford, or Sugar Hill:

• Footprint: 2,000 sq ft, roof at a 7/12 pitch → 2,000 × 1.20 = 2,400 sq ft of actual roof.
• 2,400 ÷ 100 = 24 squares.
• Add 10% waste on a straightforward gable layout → we'd order materials for about 26.4 squares (roughly 79 bundles of shingles).

For reference, most single-family homes we re-roof land at ~20–30 squares. We confirm every number on-site (or with aerial measurement) during a Free Roof Inspection, whether you're in Alpharetta, Johns Creek, Cumming, Marietta, or anywhere across Gwinnett County. True to our anti-upsell approach, we only recommend the materials your roof actually needs — never a bigger job than the damage calls for. No mystery, no padding.

How much is a square of roofing in Metro Atlanta?

An installed architectural asphalt shingle roof in Metro Atlanta costs roughly $550 to $900 per square in 2026, including materials, labor, and tear-off — about $3.50 to $6.00 per square foot. Budget 3-tab can run lower (around $380–$600 per square), but most homes in Gwinnett and North Atlanta now use architectural shingles. Shingle material alone is about $110–$170 per square (roughly $40–$70 per bundle) before labor.

Multiply per-square cost by your roof's squares and you get a ballpark total. A full asphalt replacement in the Atlanta area runs about $8,000 to $15,000, and a ~2,000-square-foot home often lands near $12,000. Metro Atlanta tends to run about 15–25% higher than rural Georgia because of labor, permits, and demand. These are estimates only — the honest truth is that the real number depends on your exact roof size, pitch, and complexity. For a deeper breakdown, see our roof replacement cost in North Atlanta guide, or ask about roof financing.

How many squares is an average house?

An average single-family home roof is about 20 to 30 squares. A small ranch is often 17 to 20 squares, while a large two-story home can reach 28 to 35 squares. The exact count always depends on pitch and roof complexity, which is why a quick measurement beats any rule of thumb. Whether you need a full roof replacement or targeted roof repairs, knowing your square count is the first step.

Frequently Asked Questions

What is a square in roofing?

A square in roofing is a unit of measurement equal to 100 square feet of roof surface, or a 10-foot by 10-foot area. Roofers measure and price materials and labor by the square instead of by the square foot because it keeps the math simple and consistent across the whole industry.

How big is a roofing square?

A roofing square covers 100 square feet of roof surface, which is the same as a 10 ft by 10 ft section. It measures the area of the roof itself, not the floor area or footprint of the house, so a steep roof contains more squares than a flat one over the same footprint.

How many square feet are in a roofing square?

There are exactly 100 square feet in one roofing square. To convert square feet to squares, divide the total roof area in square feet by 100. For example, 2,400 square feet of roof equals 24 squares.

How many bundles are in a roofing square?

There are 3 bundles in a roofing square for standard asphalt shingles, including both architectural and 3-tab styles. Heavier premium or designer shingles need 4 bundles per square, and wood shakes need about 5 bundles per square.

How much is a square of roofing?

An installed architectural asphalt shingle roof in Metro Atlanta costs roughly $550 to $900 per square in 2026, including materials, labor, and tear-off. Shingle material alone runs about $110 to $170 per square before labor. The only way to know your exact price is a free roof inspection.

How many roofing squares is an average house?

An average single-family home roof is about 20 to 30 squares. A small ranch is often 17 to 20 squares, while a large two-story home can run 28 to 35 squares depending on roof pitch and complexity.

Serving Gwinnett & North Atlanta