How to Calculate Roofing Squares and Shingle Bundles

Roofers do not price in square feet. They price in squares: one square is 100 square feet of roof. A typical house roof is 15 to 35 squares, and shingles are sold in bundles, usually three to a square. This guide shows how to get from the size of your house to the number of bundles, without climbing onto the roof.

Step 1: Find the footprint

For a simple gable or hip roof, the roof covers the footprint of the building plus the overhang. Measure the length and width of the house, and the overhang (the distance the eaves stick out, typically 12 to 24 inches). Add the overhang on both sides of each dimension. A 40 × 30 ft house with a 1 ft overhang has a footprint of 42 × 32 = 1,344 ft².

Step 2: Apply the pitch

A sloped roof is larger than the area it covers on the ground. The steeper the roof, the larger the factor. Pitch is written as rise over run: a 6/12 roof rises 6 inches for every 12 inches of horizontal run. Multiply the footprint by the slope multiplier for the pitch.

With a 6/12 pitch, the 1,344 ft² footprint becomes 1,344 × 1.118 = 1,503 ft², which is 15.0 squares.

How to find your pitch safely

From the attic: hold a level against the underside of a rafter, mark 12 inches along the level, and measure straight up to the rafter. That vertical distance in inches is the rise (the x in x/12). From the ground: photograph the gable end from straight on and use a pitch app, or compare the roofline with a known angle. Do not climb a roof you are not equipped to be on. Use the roof pitch calculator to convert between pitch, angle and slope.

Step 3: Add waste

Shingles are cut at the ridges, hips, valleys and edges, and some are lost to bad bundles. Typical waste allowances:

• 10% for a simple gable roof with few cuts.
• 15% for a hip roof, or a roof with a few valleys and dormers.
• 20% or more for a complex roof with many hips, valleys, dormers and penetrations.

Continuing the example: 15.0 squares with 10% waste is 16.5 squares. At three bundles per square that is 50 bundles.

Roof area by footprint size (6/12 pitch)

A quick reference for a 6/12 roof with 10% waste at three bundles per square:

What else goes on a roof

Shingles are only part of a roofing job. A full list usually includes:

• Underlayment: a synthetic or felt layer over the deck. A roll of synthetic underlayment typically covers about 10 squares (1,000 ft²).
• Starter strip: a row along the eaves and rakes, which is not counted in the field shingle total.
• Ridge and hip caps: sold separately, or cut from field shingles. Measure the length of the ridges and hips.
• Drip edge, flashing and ice-and-water shield: measured in linear feet, along the eaves, rakes, valleys and around chimneys and walls.
• Nails: roughly 320 per square is a common planning figure for standard nailing, and many bundles come with a recommended number. Follow the manufacturer's nailing pattern.
• Vents and pipe boots: count the roof penetrations.

Two measuring tips

• Measure each roof section separately if the house has wings, garages or porches at different pitches. Add the results.
• Do not rely on the footprint alone for complex roofs. Dormers, valleys and cross gables add area, so use the higher waste factor, or measure each plane.

If you are getting quotes, ask each roofer how they measured and what the quote includes (tear-off, disposal, decking repairs, underlayment, flashing and permits). Comparing the numbers is easier when you know how many squares the roof is.