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How Many Squares Is My Roof?

Quick answer: A roofing "square" equals 100 sq ft — divide your total roof area (including the pitch factor) by 100 to get the number of squares.

A roofing "square" is simply 100 square feet of roof. Getting your square count right is the foundation of every shingle, underlayment, and cost estimate — and you can do it from the ground.

What a square means

One square = 100 sq ft of roof surface. A 24-square roof means 2,400 sq ft of surface to cover. Shingles are wrapped and sold around this unit (3 bundles per square), and contractors quote by the square, so it is the number you want.

Step 1: Measure the footprint

From the ground, measure the length and width of the house including the roof overhangs, not just the walls. Multiply them for the footprint area. Break complex shapes (L-shapes, wings) into rectangles and add them up.

Step 2: Multiply by the pitch multiplier

Because the roof is sloped, its surface is larger than the footprint. Multiply by the pitch multiplier:

Not sure of your pitch? See Roof Pitch to Angle, or measure it with the Roof Pitch Calculator.

Step 3: Divide by 100

Worked example

A 40 ft × 30 ft footprint (with overhangs) on a 6/12 roof:

• Footprint: 40 × 30 = 1,200 sq ft
• Roof area: 1,200 × 1.118 = 1,342 sq ft
• Squares: 1,342 ÷ 100 = ~13.4 squares

Turn squares into materials

Once you have squares, the shingle and underlayment math is quick — or let the tool do it:

Roof Shingle Calculator →

For the full walk-through, see How Many Bundles of Shingles Do I Need?

Measuring without getting on the roof

You do not need to walk a roof to get a usable square count, and on anything above a 6/12 pitch you should not. Three ground-level methods, in order of accuracy:

• Measure the footprint at ground level. Pace or tape the outside walls, then add the eave and rake overhangs (typically 12–24 in each side). Multiply by the pitch multiplier. This is accurate to within a few percent on simple gable roofs.
• Determine pitch from inside the attic. Hold a level horizontally against a rafter, mark 12 in along it, and measure straight up to the rafter. That vertical measurement is your rise over a 12 in run.
• Use satellite imagery. Measure the footprint in any mapping tool's distance tool, then apply the multiplier. Good enough for a budget number, not for a final order.

Pitch multipliers

The multiplier is simply the hypotenuse of the rise-over-run triangle: √(rise² + run²) ÷ run. A 12/12 roof has 41% more surface than its footprint, which is why steep roofs cost so much more to cover than their floor plan suggests.

Waste: hips, valleys, and why 10% is often not enough

Squares tell you the surface area. They do not tell you how much material you will actually consume, because every hip and valley forces angled cuts that produce unusable offcuts.

What a square converts into

One square (100 sq ft) of standard architectural shingles is 3 bundles. Heavier designer shingles run 4–5 bundles per square, so confirm against the wrapper rather than assuming. Underlayment comes in 4-square rolls for synthetic and 2-square rolls for 15 lb felt, and you will need roughly 320 nails per square at four per shingle.

Frequently asked questions

What is a roofing square?

100 square feet of roof surface — the standard unit for estimating and selling roofing.

How many squares is a 2,000 sq ft roof?

If that's the true sloped area, 20 squares. If it's the footprint, apply the pitch multiplier first (a 6/12 roof ≈ 22.4 squares).

Do I include overhangs?

Yes — measure to the edge of the eaves and rakes, not the walls.