How many shingles do I need for my roof?

Start from your roof's total area in "squares" (1 square = 100 sq ft of roof surface). Most asphalt shingles come 3 bundles per square, so multiply your squares by 3 to get the number of bundles, then add a waste factor (typically 10-15%) to cover cuts and mistakes. This calculator does all of that from your building's footprint and roof pitch.

What is a roofing "square"?

A square is a roofing industry unit equal to 100 square feet of roof surface — 10 feet by 10 feet. Roofers and material suppliers price and order almost everything (shingles, underlayment, labor) in squares rather than raw square footage, so it's worth getting comfortable with the term.

Why is my roof area bigger than my building's footprint?

Because a sloped roof surface is always longer than the flat ground area it covers — the steeper the pitch, the bigger the difference. This calculator multiplies your building's footprint by a slope factor derived from your roof's rise and run (the same math used in our Roof Pitch Calculator) to get the true roof surface area.

Why does roof style (gable vs. hip) matter for materials?

A hip roof has sloped sections on all four sides instead of two, which means more cut edges along hips and valleys. That extra cutting typically wastes more material than a simple gable roof, so this calculator automatically adds a few extra percentage points of waste for hip roofs.

What waste factor should I use?

10% is a common baseline for a straightforward gable roof with a professional crew. Complex rooflines, steep pitches, inexperienced installers, or a hip roof style all justify pushing that closer to 15-20% — better to have a little extra than to run short mid-job and wait on a delivery.

Does this include ridge cap, flashing, or ventilation?

No. This estimate covers field shingles (the main roof surface), underlayment, and nails only. Ridge cap shingles, starter strip, flashing, drip edge, and ventilation components are typically priced and ordered separately — ask your supplier for a full materials list once you have your square count.

How much underlayment (felt) do I need?

A standard roll of 15-lb felt covers about 4 squares (400 sq ft). This calculator divides your total squares by 4 and rounds up to a whole roll count. Synthetic underlayment rolls often cover more area per roll — check your specific product's coverage rating.

Is this calculator a substitute for a professional roof estimate?

No. It gives a solid material quantity estimate for planning and budgeting, but a professional roofer measures the actual roof directly (including valleys, dormers, and skylights this calculator can't account for) and can spot structural issues a calculator never will. Use this to sanity-check a quote, not to replace one.

AI Insights

Roofing Calculator

Estimate roof area, shingle bundles, underlayment, and nails from your building footprint and roof pitch, with a cost estimate.

Building length (ft)

Building width (ft)

Roof pitch — rise (in)

Roof pitch — run (in)

Eave overhang (in)

Waste factor (%)

Roof style

Cost per bundle ($, optional)

Shingle bundles needed

16.5 squares · 1,503 sq ft roof area

Underlayment (felt)

5 rolls

Roofing nails

41.3 lbs

Estimated cost

$2,000

For a medium-sized gable roof, a standard crew of three to four professionals can typically tear off and install your new shingles in just one to two days. Because gable roofs feature straightforward triangular geometry, you will only need to account for about five to ten percent extra material to cover ridge caps and edge cuts. This makes material staging and cleanup relatively simple, usually fitting easily into a single driveway dumpster without blocking your street for long.

AI-generated insight

This estimate covers field shingles, underlayment, and nails only — it doesn't include ridge cap, starter strip, flashing, or ventilation, which most jobs also need. Always round up to full bundles and buy a little extra to cover cutting waste and future repairs.

How to use the roofing calculator

1
Enter your building length and width in feet.
2
Enter your roof pitch as rise and run (a 6/12 pitch rises 6 inches for every 12 inches of run).
3
Set your eave overhang, choose gable or hip style, and adjust the waste factor.
4
Bundles, underlayment rolls, nail weight, and an optional cost estimate update instantly.

How roof area and squares are calculated

A roofing 'square' is 100 sq ft of roof surface — always more than the flat footprint below it, because the surface follows the slope.

Slope factor: √(rise² + run²) ÷ run — the same formula used in our Roof Pitch Calculator. A 6/12 pitch gives a slope factor of about 1.118, meaning the roof surface is about 11.8% larger than the flat footprint.

Worked example: a 40 ft × 30 ft building with a 6/12 pitch, 12-inch eave overhang, gable roof, and 10% waste: the footprint expands to 42 ft × 32 ft with overhang, giving a roof area of about 1,503 sq ft. That's 16.5 squares, which rounds up to 50 bundles of shingles (16.5 × 3, rounded up), 5 rolls of felt underlayment, and about 41 lbs of roofing nails.

Gable vs. hip roofs and waste factor

Roof style	Effective waste (10% base)	Bundles (same 1,503 sq ft example)
Gable (two slopes)	10%	50
Hip (four slopes)	15%	52

The extra 5% for hip roofs reflects the additional angled cuts at every hip and valley. Highly cut-up rooflines — dormers, intersecting gables, multiple valleys — can justify pushing waste even higher than the hip default; when in doubt, round up.

What this estimate doesn't include

This calculator covers the three materials that scale directly with roof area — field shingles, underlayment, and nails. A complete roofing materials list also typically needs:

Ridge cap shingles, priced separately and based on total ridge length, not roof area.
Starter strip along the eaves and rakes.
Flashing at valleys, chimneys, walls, and any roof penetrations.
Drip edge along the perimeter.
Ventilation components like ridge vents or box vents.

Bring your square count from this calculator to a roofing supplier for a complete materials quote, or if you're also planning the framing underneath, check our Roof Pitch Calculator for rafter length and roof angle.

Frequently asked questions

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