Roofing Calculator
Roofing is measured in squares — 100 square feet each. Enter your roof's footprint and pitch and this gives the squares, the shingle bundles, and the true (sloped) roof area.
Roofing squares
16.8squares
- Shingle bundles
- 56 bundles
- Roof area
- 1,677 sq ft
How it’s calculated
A pitched roof is bigger than its footprint: roof area = footprint × √(12² + rise²) ÷ 12, where rise is the pitch in 12. Squares = roof area ÷ 100. Bundles = squares × (1 + waste) × bundles per square, rounded up — most shingles run about 3 bundles to a square, but always check the wrapper.
Worked example
1,500 sq ft footprint at 6/12 pitch: the pitch multiplier is √(144 + 36) ÷ 12 ≈ 1.118, so roof area ≈ 1,677 sq ft = 16.8 squares. At 3 bundles/square + 10% waste: 16.8 × 1.10 × 3 ≈ 56 bundles.
FAQs
- What is a roofing square?
- 100 square feet of roof surface — the unit roofers price and order by. A 2,000-square-foot roof is 20 squares.
- Why does pitch matter?
- A steeper roof has more surface than the ground it covers. A 6/12 pitch adds about 12% to the footprint; a 12/12 (45°) adds about 41%. That's the multiplier in the formula.
- How many bundles per square?
- About 3 for standard 3-tab and most architectural shingles, but heavier designer shingles run 4–5 — the wrapper states it. This calculator lets you set that number. Buy starter strip and ridge cap separately.
- Will this work for a complex or low-slope roof?
- The footprint × pitch conversion assumes a simple gable; lots of hips, valleys, and dormers add surface area and cutting waste, so push the waste above 10% for a cut-up roof. And below about 2-in-12 you're out of shingle territory — low slopes need a membrane or rolled roofing, not shingles.
Sources
- Roofing square = 100 sq ft (convention). Pitch multiplier = √(12² + rise²) ÷ 12 (geometry). Bundles per square is product-specific (≈3 typical; from the wrapper) — entered, not assumed.