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Roof Square Calculator

Have the area? Get squares, bundles and the list.

The area here is up the slope, not the footprint.

1,341.6 ft²

Cutting waste on the covering — the shingles, or the metal panels. The makers allow 10% on a gable roof and 15% on a hip, where every course runs into a hip at an angle; CertainTeed's own manual says 10% is generous on a large simple roof. It moves the covering only — the starter, the cap, the drip edge and the underlayment are cut to length, not off a square.

This page recalculates as you type. There is no Calculate button.

Answer

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Roofing squares

13.42 squares

1,341.6 ft² of roof, 13.42 squares, 45 bundles

Bundles of shingles 45 bundles
Roof area, up the slope 1,341.6 ft²
What the list comes to $2,207.00
More numbers
Footprint, on the ground 1,341.6 ft²
Slope factor 1
Bundles of starter 0 bundles
Sticks of drip edge 0 sticks
Rolls of underlayment 2 rolls
Nails 3,435 nails

Buying noteAn area typed in is a roof measured up the slope, not an outline, so it has no eave, rake or ridge. The shingles, the underlayment and the nails count it; the starter, the ridge cap and the drip edge cannot. Enter the roof as a footprint and a pitch if you need those.
Buying noteNo ice barrier is on this list. The code requires one where your town's table says so — look up Table R301.2 for where you are, and switch it on if it says yes.

Breakdown

Plane Measurements Qty Area on the slope Share
Area 1 1,341.6 Add ×1 1,341.6 ft²

What to buy

Buying noteAn area typed in is a roof measured up the slope, not an outline, so it has no eave, rake or ridge. The shingles, the underlayment and the nails count it; the starter, the ridge cap and the drip edge cannot. Enter the roof as a footprint and a pitch if you need those.
Buying noteNo ice barrier is on this list. The code requires one where your town's table says so — look up Table R301.2 for where you are, and switch it on if it says yes.

Ways to buy the shingles

Every bundle is worked out, each rounded up to whole bundles; pick the one you will buy. The three are different shingles, not three sizes of one, so a mix means two products on one roof — buy a mix only if you meant to.

45 × bundles of HDZ Bundles 45 Left over 24.09 ft² Weight 3,501 lb Cost $1,890.00 Reference price $42.00. Type your store's.
45 × bundles of Oakridge Bundles 45 Left over 0.24 ft² Weight 3,240 lb Cost $1,710.00 Reference price $38.00. Type your store's.
45 × bundles of Landmark Bundles 45 Left over 24.09 ft² Weight 3,375 lb Cost $1,980.00 Reference price $44.00. Type your store's.

Shopping list

45 45 × bundles of HDZ $1,890.00
2 2 × rolls of synthetic $256.00 Reference price $128.00. Type your store's.
5 4 × 5 lb boxes of nails + 1 × 1 lb boxes of nails $61.00 Reference price $78.00. Type your store's. Reference price $14.00. Type your store's. Reference price $5.00. Type your store's.
Ticked items $2,207.00

Untick what you already have. Each row has its price beside it — type what your store charges.

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Standards

We hold the criteria and the clause, not the wording of the standard.

Not checked IRC 2021 · R905.2.2

No plane here has measurements that make a roof.

Not checked IRC 2021 · R905.2.2

No plane here has measurements that make a roof.

Not checked IRC 2021 · R905.2.8.5

No plane here has measurements that make a roof.

Not checked IRC 2021 · R905.1.2

No plane here has measurements that make a roof.

How this was worked out

Every number below is yours. Each constant links to the row where you can change it.

Area 1 1,341.6 1,341.6 ft²
Squares of roof 1,341.6 ft² ÷ 100 ft² 13.42 squares

Change:A roofing square

With cutting waste 1,341.6 ft² × (1 + 10%) 1,475.76 ft²
Bundles to buy 1,475.76 ft² ÷ 33.33 ft² 45 × bundles of HDZ · 24.09 ft² over

Change:GAF HDZ bundle coversOC Oakridge bundle coversCT Landmark bundle covers

Starter course 0" ÷ 0 lf

Change:GAF Pro-Start bundle runsOC starter bundle runs

Drip edge 0" ÷ (10' − 2") 0 sticks

Change:A stick of drip edgeDrip edge lap

Underlayment 1,341.6 ft² ÷ (1,001 ft² × (1 − 10%)) 2 rolls

Change:Synthetic roll coversLaps take off a roll

Nails 13.42 squares × 256 3,435 nails → 4 × 5 lb boxes of nails + 1 × 1 lb boxes of nails

Change:Nails a square

What it comes to 45 × $42.00 + 2 × $128.00 + 4 × $14.00 + 1 × $5.00 $2,207.00

Assumptions

Every one of these is editable. Change one and the answer changes with it.

Assumption Value Confidence
A roofing squareA roofing square is 100 ft² by the trade's definition; every shingle wrapper and every estimate is quoted in them. ≈ ft²/square Trade convention
GAF HDZ bundle coversGAF Timberline HDZ: 33.33 ft² a bundle, three bundles to the square, from the Home Depot listing. ft²/bundle From a data sheet or an agency document
OC Oakridge bundle coversOwens Corning Oakridge and Duration: 32.8 ft² a bundle. Three of them cover 98.4 ft², not 100, which is why this page never counts three bundles to the square. ft²/bundle From a data sheet or an agency document
CT Landmark bundle coversInferred, not printed: the CertainTeed Landmark data sheet gives 66 shingles to the square, and three bundles to the square is the trade's convention, so a bundle covers 100/3 ft². The sheet does not state a coverage per bundle. ~ ft²/bundle Derived or single-supplier
GAF Pro-Start bundle runsGAF Pro-Start starter strip: 120.33 linear feet a bundle, from GAF's own product page. lf/bundle From a data sheet or an agency document
OC starter bundle runsOwens Corning Starter Strip Plus: 105 linear feet a bundle, data sheet dms/10011118. lf/bundle From a data sheet or an agency document
Seal-A-Ridge bundle runsGAF Seal-A-Ridge ridge cap: 25 linear feet a bundle, from the Home Depot listing. lf/bundle From a data sheet or an agency document
OC ProEdge bundle runsOwens Corning ProEdge ridge cap: 33 linear feet a bundle, from the Home Depot combination listing. lf/bundle From a data sheet or an agency document
A stick of drip edgeDrip edge is sold in 10 ft sticks in every profile. Gibraltar Building Products catalog 2026 (AWC020926B) page 5. ft From a data sheet or an agency document
Drip edge lapDrip edge sticks lap at least 2 in, so a 10 ft stick covers 9 ft 10 in. JLC on IRC R905.2.8.5, which requires drip edge at eaves and rakes but gives the lap as a minimum rather than a number. ≈ in Trade convention
Synthetic roll coversOwens Corning ProArmor synthetic underlayment: 1,001 ft² a roll, from the Home Depot combination listing, read 14/10/2026. ft²/roll From a data sheet or an agency document
Laps take off a rollWhat the head and side laps take off a roll's printed area. A 36 in felt lapped 2 in at the head over a 36 in exposure loses about a tenth; synthetic sheets print a lap line at much the same place. An editable single number because the exact loss depends on the exposure the installer works to. ~ ratio Derived or single-supplier
Nails a squareGAF: 256 nails a square. The figure is theirs; how it divides over shingles and courses is not stated and is not inferred here. nails/square From a data sheet or an agency document
Shallowest pitch for shinglesThe floor for asphalt shingles: at this pitch and above they may be used, and from here up to the next limit the underlayment doubles. IRC R905.2.2 states both. CertainTeed's Landmark data sheet is one step stricter - "greater than 2:12" - so a roof at exactly 2:12 passes here and not on their sheet; this box is where you put their figure. rise per 12 From a data sheet or an agency document
Double underlayment belowBelow this pitch, and at or above the shallowest pitch for shingles, the underlayment has to be doubled. IRC R905.2.2; CertainTeed's Landmark data sheet states the same range. rise per 12 From a data sheet or an agency document
Hire a roofer aboveWhere a roof stops being walkable without staging. Not a code limit: it is the slope at which this page says to get a quote rather than climb up. 6:12 itself is walkable, so the warning starts above it. ≈ rise per 12 Trade convention
Cutting waste, hip15% on a hip roof: four planes means a cut at every hip. Same sources as the gable figure. A hip roof needs no second 'hip factor' on its area - the slope factor already covers the whole surface - only more cutting. ≈ ratio Trade convention

A square is 100 square feet

Roofing is quoted in squares. One square is 100 square feet of roof — not of footprint, and not of anything measured on the ground. A 1,341.6 square foot roof is 13.42 squares, and that is the figure a supplier, an estimator and a dumpster rental all work from.

If you already have the area — off an aerial measurement report, a contractor's estimate, or your own figuring — type it here and get the squares and the rest of the list. The area this page wants is the area up the slope: a measurement report has already applied the pitch, so there is nothing left to multiply.

Roof area Squares Bundles at 10% Rolls of synthetic
800 ft²8.00271
1,200 ft²12.00402
1,600 ft²16.00532
2,400 ft²24.00803
3,200 ft²32.001064

What an area cannot tell you

An area has no outline. The starter course, the ridge cap and the drip edge are all counted from edge lengths — eaves, rakes, ridges, hips — and an area typed in has none of them, so those rows come out as nothing and the page says so above the list. The shingles, the underlayment and the nails go by area and are right.

If your report gives the edge lengths too — most of them do, under names like "eave", "rake", "ridge" and "hip" — the roofing calculator works them out from a footprint and a pitch instead, and you can check its figures against the report's.

Squares and the figures around them

A square of architectural shingles weighs about 230 to 250 pounds, so a 20 square roof is between 4,600 and 5,000 pounds of material going up a ladder, and the same coming down if you are tearing off. Three bundles make roughly a square, and a bundle is 70 to 80 pounds — one at a time is the limit for most people.