Roofing Calculator
Roof area, roofing squares, and shingle bundles from two measurements you can take from the ground — the house footprint and the roof pitch.
incl. eave overhangs
Waste
15% for hips/valleys
Roof area (+10%)
1,476
sq ft (×1.118 pitch)
Roofing squares
14.8
1 square = 100 sq ft
Shingle bundles
45
3 bundles per square
Uses the footprint × pitch-multiplier method for a standard gable roof — measure the footprint to the eave edges, not the walls. Complex rooflines with hips, valleys, and dormers add cuts; use 15% waste and expect a contractor's measure to differ slightly.
Squares, Pitch, and the Multiplier
Roofing is sold by the “square” — 100 square feet — and a sloped roof is always bigger than the footprint beneath it. The pitch multiplier converts one to the other: a 6/12 roof (6 inches of rise per foot of run) is √(1 + 0.5²) = 1.118 times its footprint. Standard three-tab and architectural shingles ship three bundles to the square.
Pitch multipliers
Roof area = footprint × √(1 + (pitch/12)²) × (1 + waste) 3/12 → ×1.031 6/12 → ×1.118 9/12 → ×1.250 4/12 → ×1.054 7/12 → ×1.158 12/12 → ×1.414 5/12 → ×1.083 8/12 → ×1.202 Example: 40×30 footprint, 6/12 pitch, 10% waste: 1,200 × 1.118 × 1.10 = 1,476 sq ft ≈ 14.8 squares ≈ 45 bundles
Frequently Asked Questions
How many bundles of shingles make a square?
Three bundles per 100 sq ft square for standard three-tab and most architectural shingles — a bundle is sized so one person can carry it up a ladder. Heavier premium and specialty shingles can run 4–5 bundles per square; the wrapper states the coverage.
How do I measure my roof's pitch from the ground or attic?
In the attic: hold a level horizontally against a rafter, measure 12 inches along it, then measure straight down to the rafter — that vertical distance is the pitch (6 inches = 6/12). Phone level apps laid on a gable end work too. From the ground, count it against the 45° benchmark: a 12/12 roof is exactly 45°.
How many squares is a typical house roof?
Most US single-family homes land between 17 and 25 squares (1,700–2,500 sq ft of roof). A 1,500 sq ft single-story ranch with a 4/12 pitch is about 17 squares; two-story homes have roughly half the roof of a one-story home with the same floor area, since the footprint is smaller.
Does this work for hip roofs or just gables?
The footprint × pitch-multiplier math holds for any roof where all faces share the same pitch — including simple hips, since the geometry trades ridge length for slope area evenly. What changes is waste: hips and valleys generate more cut shingles, so use 15% instead of 10%.