Roofing Squares Calculator
Roofing squares and shingle bundles from footprint and pitch.
Input sheet
DIY at your own risk. Calcora's calculators and guides are general estimates and information only — not professional, engineering, legal, or safety advice. Always verify local building codes and permit requirements, and hire a licensed pro for electrical, gas, plumbing, structural, or any work you're not fully comfortable doing yourself.
Roofers measure in 'squares' — 100 square feet of roof surface — and your roof's slope means its true area is bigger than the footprint you see from above. This calculator applies a pitch multiplier so your shingle count is right.
How it works
Footprint area times a pitch multiplier gives true roof area. 100 sq ft = 1 square; ~3 bundles cover a square.
A flat footprint understates a sloped roof's surface. The calculator multiplies footprint area by a pitch factor (1.0 for flat, up to 1.414 for a steep 12/12) to get true surface area, divides by 100 for roofing squares, and figures roughly 3 bundles of shingles per square.
Pitch is expressed as rise-over-run: a 6/12 roof rises 6 inches for every 12 inches of horizontal run. Steeper roofs have dramatically more surface area — and are far harder to walk, which affects labor.
Roof area = footprint length × width × pitch factor; squares = roof area ÷ 100; bundles = squares × 3, rounded up.
Worked examples
A 40 ft × 30 ft ranch footprint with a 6/12 pitch. → About 13.4 squares, or 41 bundles.
40 × 30 = 1,200 sq ft footprint × 1.118 ≈ 1,342 sq ft of roof ÷ 100 ≈ 13.4 squares × 3 ≈ 41 bundles.
A 24 ft × 24 ft garage with a 6/12 pitch. → About 6.4 squares, or 20 bundles.
24 × 24 = 576 sq ft × 1.118 ≈ 644 sq ft ÷ 100 ≈ 6.4 squares × 3 ≈ 20 bundles.
Tips & gotchas
- Three bundles cover one square of standard architectural shingles — heavier designer shingles can run four bundles per square, so confirm with the product.
- Add material for hips, ridges, and starter strips; those use specialty shingles the per-square count doesn't include.
- Buy 10–15% extra on complex roofs with many valleys and dormers, where waste from cuts climbs fast.
- Measure the footprint from the eaves, not the exterior walls — the overhang is real roof area you'll be covering.
FAQ
What is a roofing square?
It's the trade unit for roofing: 100 square feet of roof surface. Shingles, underlayment, and labor are all quoted per square, which is why the calculator converts your area into them.
How do I find my roof's pitch?
Measure how many inches the roof rises over a 12-inch horizontal run. A level and a tape against a rafter, or a measurement off the gable end, gives you the rise-over-run to pick from the list.
Does steeper pitch really need more shingles?
Yes — a 12/12 roof has about 41% more surface than its footprint, while a flat roof has none. The pitch multiplier captures that extra area so you don't under-order.
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