How to Measure a Roof for Shingles: Squares, Pitch and Bundles
Learn what a roofing square is, how pitch changes the roof's surface area, and how to turn a house footprint into a bundle count with a worked example.
Roofing is priced and sold in squares and bundles, which can be confusing the first time. This guide explains the units, shows how pitch changes the area, and walks through a complete estimate.
What is a roofing square?
A roofing square is 100 square feet of roof surface. Shingles are packaged in bundles, and standard asphalt shingles are commonly sold at about three bundles per square. Some thicker products use more, so check the package.
Why pitch matters
A roof is larger than the footprint of the house under it, and a steeper roof is larger still. Pitch is written as rise over run, such as 6/12, meaning the roof rises 6 inches for every 12 inches of horizontal distance. The roof's surface area equals the footprint times a pitch factor, which is √(1 + (rise ÷ 12)²).
- 4/12 pitch: factor 1.054
- 6/12 pitch: factor 1.118
- 8/12 pitch: factor 1.202
Worked example: a 30 × 40 foot house with a 6/12 roof
- Footprint: 30 × 40 = 1,200 square feet
- Roof area: 1,200 × 1.118 = 1,342 square feet, or 13.4 squares
- Add 10% for waste, starter and ridge pieces: 14.8 squares
- Bundles at 3 per square: 14.8 × 3 = 45 bundles
Waste and complexity
A waste allowance of 10 to 15 percent is typical for a simple roof. Hips, valleys, dormers and chimneys add cuts and waste, so complex roofs need more. For anything beyond a simple gable, a roofer's measurement or an aerial roof measurement is more precise than a footprint estimate.
Measure safely
You do not need to climb the roof. Measure the footprint from the ground, include any overhangs, and estimate the pitch from the attic rafters or from photos. Never walk a steep or wet roof.
What is not included
Underlayment, flashing, drip edge, ridge caps, nails and tear-off of the old roof are separate costs. Our calculator estimates shingle bundles only.