Roofing Calculator
Calculate roofing squares and shingle bundles from your roof footprint and pitch.
What you need
42
Bundles needed — Rounded up, waste allowance included.
- Area to cover
- 1,200.0 sq ft
- Area including waste allowance
- 1,391.3 sq ft
- Roofing squares
- 13.9
One square is 100 sq ft. This is how roofers price the job.
Estimates for planning. Confirm quantities with your supplier before ordering — see the assumptions below for the figures used.
How to use the roofing calculator
Roofers work in squares — 100 square feet each — and the roof is always bigger than the building beneath it because of the pitch. Enter your footprint and pick your roof slope, and this calculator applies the pitch multiplier for you.
What this calculator assumes
Every estimate depends on figures that vary by supplier and conditions. These are the ones used here, so you can sanity-check the result against your own quote.
- Coverage per bundle is taken from your entry above — always check the actual packaging, because it varies by product.
- A 10% waste allowance is applied by default. Increase it for diagonal layouts, busy patterns or rooms with lots of corners.
- Bundles are rounded up to whole units.
- The pitch multiplier converts the flat footprint into actual roof surface. It does not account for overhangs, dormers or a complex roof outline — measure those separately and use the 'total area' mode.
- Three bundles per square is standard for architectural asphalt shingles. Some premium and specialty shingles need four or five bundles per square.
- Underlayment, ice and water shield, drip edge, ridge vent, starter strip and nails are not included.
- Re-roofing over an existing layer, tear-off disposal and any deck repair are separate costs — and local code limits how many layers are allowed.
Frequently asked questions
How many bundles of shingles are in a square?
Three, for standard architectural and three-tab asphalt shingles — each bundle covers about 33.3 square feet. Heavier premium shingles can be four or five bundles per square, so check the wrapper before you multiply.
What is a roofing square?
One hundred square feet of finished roof surface. It is the unit roofers quote in, so a 2,000 square foot roof is 20 squares. Note that is 20 squares of roof surface, not of building footprint — the pitch makes the roof larger.
How do I find my roof pitch?
Hold a level horizontally against the roof surface, measure 12 inches along it, then measure straight down to the roof at that point. That drop in inches is your rise: a 6 inch drop is a 6/12 pitch. From the ground, comparing the roof line to a photo pitch guide gets you close enough for estimating.
Should I re-roof myself?
Roofing is the most dangerous common DIY job — fall height, steep pitch and heavy loads. It is also where a small mistake causes water damage you will not see for a year. This calculator is useful for checking a quote is in the right ballpark; the work itself is worth paying for on anything above a low-slope shed roof.
How much extra should I buy?
The default here is 10%. Buying a little extra from the same batch is cheap insurance — colours and lots shift between production runs, so a mid-project top-up rarely matches. Keep the offcuts for future repairs.
How do I handle an L-shaped or irregular room?
Split it into rectangles, work out each one separately and add the results. Measure at the widest point of each section and ignore small alcoves unless you are covering them too.
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