Roofing › Shingle calculator
Shingle calculator: bundles, squares and nails for an asphalt roof
Enter the building footprint and the roof pitch, or the roof area if you already have it, and pick the shingle type. You get the roofing squares to buy, the bundles, the number of shingles, the nails, the underlayment rolls and, with the ridge and eave lengths, the hip and ridge cap, starter strip and drip edge. Bundles and pieces per square come from the manufacturers' own data sheets, and every code figure the tool warns about is tied to its section of the 2021 IRC.
Shingles are bought by the square, 100 sq ft of roof surface, and the surface is bigger than the footprint by the slope factor: roof area = footprint × √(rise² + 12²) ÷ 12, then squares = roof area ÷ 100, and bundles are squares times the waste multiplier times the bundles per square, rounded up. A 40 x 30 ft footprint at 6/12 is 1,341.6 sq ft, 13.4 squares, 14.8 squares to buy with 10% waste, and 45 bundles of a 3-bundle architectural shingle.
Three bundles per square is the common case, not a rule: heavyweight and premium shingles ship 4 or 5 to the square, and the wrapper says which. The manufacturer coverage table below lists the sheet figures, and the FAQ answers the bundle, square and nail questions that come up most.
Roof shingle calculator: squares, bundles, nails and underlayment
Use it as a roof shingle calculator, a shingle roof calculator, a roofing shingles calculator, an asphalt shingle calculator or an architectural shingle calculator: the arithmetic is the same and only the bundles and pieces per square change with the type. It is free and needs no sign-up. The first result is the squares to buy with waste in; the rows under it separate the measured roof from what goes on the order, so you can see which number has waste in it and which does not.
At its defaults, a 40 x 30 ft footprint at 6/12 with an architectural shingle, the tool returns 14.8 squares to buy, a roof area of 1,341.6 sq ft, 13.4 measured squares, a slope factor of 1.1180 at 26.57°, 45 bundles, 945 shingles, 3,780 nails at 4 per shingle and 2 synthetic rolls. Enter 40 ft of ridge and 140 ft of eave and rake and it adds 2 bundles of cap, 2 bundles of starter and 15 pieces of drip edge.
| Input | What to enter | Default |
|---|---|---|
| I know | The footprint plus the pitch, or the roof surface area if you have measured it or have a report | footprint + pitch |
| Footprint length, footprint width | Eave to eave and rake to rake at the outside of the roof, overhangs included; feet and inches are accepted (40' 6") | 40 ft, 30 ft |
| Roof pitch | Rise per 12 in of run from the list, or Other pitch and a rise of your own; flat is offered so the tool can refuse it | 6/12 |
| Roof surface area | Shown when you know the area: the sloped surface in sq ft, pitch already in it | 2,000 sq ft |
| Shingle type | 3-tab, architectural (laminated, dimensional), heavyweight or premium; sets bundles and pieces per square | Architectural |
| Nails per shingle | 4, the IRC minimum, or 6 where the wrapper calls for it in high wind or on steep slopes | 4 |
| Underlayment | Synthetic 10-square roll, #15 felt, #30 felt or none | Synthetic |
| Ridge + hip length | Total length of ridge and hips to be capped; leave 0 to skip the cap row | 0 |
| Cap product | Shown when a ridge length is entered: cut 3-tab or 12 x 36 in cap, 6⅔ in exposure cap, or 8 in exposure cap | 33 lin ft per bundle |
| Eave + rake length | Total length of every edge that gets starter and drip edge; leave 0 to skip | 0 |
| Starter product | Shown when an eave length is entered: pre-cut starter or 3-tab shingles cut for starter | Pre-cut, 100 lin ft |
| Waste allowance | Added to shingles, pieces and nails only; 10 for a plain gable, 15 for hips and valleys, 20 for a cut-up roof | 10% |
Which rows carry waste and which do not
Squares to buy, bundles, shingles and nails carry the waste allowance; the line under the result says so. Roof area and measured squares never do, because waste is a purchasing allowance and not a change to the roof. Underlayment, cap, starter and drip edge are counted from their own lengths without the shingle waste: a roll of underlayment is already rated before laps, and a bundle of cap covers a measured length of ridge. Switch the waste to 0 and the squares to buy drop to 13.4 and the bundles to 41; at 15% they are 15.4 and 47, at 20% 16.1 and 49.
How to calculate shingles by hand: footprint, slope factor, squares, bundles
The steps below are what the tool runs, shown for its default 40 x 30 ft footprint at 6/12 so you can check them with a pencil.
Roof area from the footprint and the pitch
Multiply the footprint: 40 × 30 = 1,200 sq ft. A 6/12 roof rises 6 in for every 12 in of run, so each foot of run is √(6² + 12²) ÷ 12 = 1.118 ft of rafter, and the surface is 1,200 × 1.118 = 1,341.6 sq ft. That is the figure the tool prints as roof area; the factor is also called the pitch multiplier, and it is the one step a shingle estimator adds to plain area. For a gable roof the footprint method is exact if the footprint includes the overhangs; for hips, valleys, dormers and roofs with several pitches, measure each plane or use the roof area calculator (planned) and enter the surface area directly.
Squares, bundles, pieces and nails
A roofing square is 100 sq ft of roof surface, so 1,341.6 ÷ 100 = 13.416 squares. Add the waste as a multiplier and keep the decimals: 13.416 × 1.10 = 14.76, which the tool prints as 14.8. Bundles come from the unrounded figure: 14.76 × 3 = 44.27, rounded up to 45. Rounding the squares to a whole number first and then multiplying is how a 16.2-square roof becomes 51 bundles instead of 49; round once, at the end, on the quantity you buy. Pieces follow the same path with the pieces per square from the data sheet: 14.76 × 64 = 945 architectural shingles, and at 4 nails each that is 3,780 nails.
Footprint, floor area and roof area are three different numbers
The square footage of a house is its floor area, and a two-story house of 2,000 sq ft has a footprint near 1,000 sq ft. The footprint is the ground the roof covers, overhangs included. The roof area is the footprint stretched by the slope factor, and it is the only one of the three that shingles are bought by. The table gives the factor for each pitch and what 1,000 sq ft of footprint becomes; the roof pitch calculator (planned) finds the pitch from a rise and run, and the roof pitch to degrees chart (planned) has the angles.
| Pitch | Angle | Slope factor | Roof area per 1,000 sq ft of footprint |
|---|---|---|---|
| Flat (0/12) | 0.00° | 1.0000 | 1,000 sq ft |
| 1/12 | 4.76° | 1.0035 | 1,003 sq ft |
| 2/12 | 9.46° | 1.0138 | 1,014 sq ft |
| 3/12 | 14.04° | 1.0308 | 1,031 sq ft |
| 4/12 | 18.43° | 1.0541 | 1,054 sq ft |
| 5/12 | 22.62° | 1.0833 | 1,083 sq ft |
| 6/12 | 26.57° | 1.1180 | 1,118 sq ft |
| 7/12 | 30.26° | 1.1577 | 1,158 sq ft |
| 8/12 | 33.69° | 1.2019 | 1,202 sq ft |
| 9/12 | 36.87° | 1.2500 | 1,250 sq ft |
| 10/12 | 39.81° | 1.3017 | 1,302 sq ft |
| 11/12 | 42.51° | 1.3566 | 1,357 sq ft |
| 12/12 | 45.00° | 1.4142 | 1,414 sq ft |
| 14/12 | 49.40° | 1.5366 | 1,537 sq ft |
| 16/12 | 53.13° | 1.6667 | 1,667 sq ft |
| 18/12 | 56.31° | 1.8028 | 1,803 sq ft |
The tool offers flat and 1/12 so that it can refuse them: asphalt shingles are not permitted below 2/12 (IRC R905.2.2), and from 2/12 up to 4/12 the underlayment goes on in two layers. Both are printed as warnings, with the two-layer roll count worked in, when those pitches are selected.
Bundles per square and shingles per bundle by manufacturer
Most answers to how many bundles of shingles in a square say three, and for 3-tab and standard architectural shingles that is what the sheets say. The pieces per square are what change: 80 for a 12 x 36 in 3-tab, 64 to 66 for a laminated shingle, 56 to 60 for the larger formats, 90 for a premium shake-look shingle at a 4 in exposure. The table is taken from the product data sheets and spec pages as published; it names the product so you can check the wrapper against it, and the wrapper governs where the two differ.
| Product | Type | Size and exposure, in | Pieces | Bundles | Coverage or note |
|---|---|---|---|---|---|
| GAF Timberline HDZ | architectural | 13¼ x 39⅜ at 5⅝ | 64 | 3 | not printed on the sheet; 256 nails per square at 4 |
| GAF Royal Sovereign | 3-tab | 12 x 36 at 5 | 79 | 3 | not printed on the sheet; 316 nails per square at 4 |
| Owens Corning TruDefinition Duration | architectural | 13¼ x 39⅜ at 5⅝ | 64 | 3 | 98.4 sq ft per 3 bundles |
| Owens Corning Oakridge | architectural | 13¼ x 39⅜ at 5⅝ | 64 | 3 | 98.4 sq ft per 3 bundles; not less than 20 shingles per bundle |
| Owens Corning Supreme | 3-tab | 12 x 36 at 5 | 80 | 3 | 100 sq ft per 3 bundles; not less than 26 shingles per bundle |
| CertainTeed Landmark and Landmark PRO | architectural | 13¼ x 38¾ at 5⅝ | 66 | 3 (listings) | 217 to 240 lb per square |
| CertainTeed Presidential Shake | premium | 14¼ x 40 at 4 | 90 | not on the sheet | 350 lb per square (Shake), 468 lb (Shake TL) |
| IKO Cambridge and Dynasty | architectural | 13¾ x 40⅞ at 5⅞ | 60 | 3 | 33⅓ sq ft per bundle, 20 shingles per bundle |
| IKO Marathon Plus AR | 3-tab | 13¼ x 39⅜ at 5⅝ | 65 | about 3 | 32.3 sq ft per bundle, 21 shingles per package; metric size |
| TAMKO Heritage | architectural | 13¼ x 39⅜ at 5⅝ | 64 | 3 | 98.4 sq ft per sales square of 20 + 22 + 22 shingles |
| Malarkey Vista | architectural | 13¼ x 38⅞ at 5⅝ | 66 | 3 | 100 sq ft per 3 bundles |
| Atlas Pinnacle Pristine | architectural | 14 x 42 at 6 | 56 | not on the sheet | 130 mph with 4 nails |
| GAF Woodland | heavyweight | — | 56 | 4 | from the maker's guidance, not a data sheet |
| GAF Grand Sequoia | premium | — | — | 5 | from the maker's guidance, not a data sheet |
Why three bundles cover 98.4 sq ft and not 100
Coverage is pieces times exposed area. A 13¼ x 39⅜ in laminated shingle at a 5⅝ in exposure covers about 221.5 sq in; 64 of them cover about 14,175 sq in, which is 98.4 sq ft, and that is the figure printed on the sheets that print one. A 12 x 36 in 3-tab at 5 in covers 180 sq in, and 80 cover 14,400 sq in, exactly 100. One maker packs 60 larger shingles to reach 100 sq ft per three bundles and prints 33⅓ sq ft per bundle. The tool works in squares and bundles per square, as the trade orders, so a 98.4 sq ft square is treated as a square; on a 20-square roof the difference is 32 sq ft, inside any waste allowance.
How many square feet does a bundle cover
One third of a square for a 3-bundle shingle: 33.3 sq ft, or 32.8 sq ft where the three bundles are rated at 98.4. A bundle is close to one 4 x 8 ft sheet of roof sheathing, which is a quick check on a sheathed roof: count the sheets and you have the bundles at 3 per square, before waste. Heavyweight shingles at 4 per square cover 25 sq ft per bundle and premium shingles at 5 per square cover 20. The long form of bundles, squares and coverage is in shingle bundles, squares and coverage.
Waste factor for shingles: gable, hip and cut-up roofs
A hip roof over the same footprint at the same pitch has exactly the same surface area as a gable roof, so the difference between the two is not area but waste. The hip roof area calculator (planned) prints that arithmetic both ways. Every hip and valley is a diagonal cut across a shingle, and the triangle that falls off is rarely reusable; a trade author figures about two extra shingles for every linear foot of valley, which on a 16 ft valley is a bundle. Rake edges lose an offcut on every course. Manufacturer guidance is 10 to 15% in general terms; an experienced crew on a simple roof runs lower, and an insurance estimate may allow less than a roofer does.
| Roof | Waste | Why | Squares to buy | Bundles |
|---|---|---|---|---|
| Plain gable, no valleys | 10% | rake cuts on two ends and the ridge; a few damaged pieces | 14.8 | 45 |
| Hip roof, or a gable with valleys or dormers | 15% | every hip and valley is cut on the diagonal, and the offcuts are too short to reuse | 15.4 | 47 |
| Cut-up roof: several hips and valleys, dormers, turrets | 20% | diagonal cuts on most planes, short runs, color matching across lots | 16.1 | 49 |
Whether a number already has waste in it is the question behind most arguments over an order. A roof measured at 33 squares and billed at 38 is a 15% allowance, not an error, and a delivery of 45 squares against a 50-square bid is a shortage only if the bid was already a to-buy figure. The tool prints measured squares and squares to buy as separate rows so both numbers are on the page at once. Underlayment is not inflated by the shingle waste; its roll rating already allows for the laps on a normal roof.
Starter strip, ridge cap and drip edge: linear feet per bundle
The field shingles are only the first line of the order. Starter runs along every eave and, on most roofs, every rake; cap covers every hip and ridge; drip edge goes on every eave and rake under the IRC. All three are bought by length, so the tool takes the ridge and hip total for cap and the eave and rake total for starter and drip edge, and divides by what a bundle covers. The coverages are from the product data sheets; the wrapper governs.
| Product | Use | Exposure, in | Pieces per bundle | Lin ft per bundle |
|---|---|---|---|---|
| 3-tab shingles cut at the tab cutouts (26 per bundle) | hip and ridge cap | 5 | 78 caps | 32.5 (the tool uses 33) |
| Owens Corning ProEdge | hip and ridge cap | 6 | 66 | 33 |
| CertainTeed Mountain Ridge, 12 x 36 in | hip and ridge cap | 5 | three per shingle | 30 |
| GAF Seal-A-Ridge | hip and ridge cap | 6⅔ | 45 | 25 (4 bundles per 100 ft) |
| GAF TimberTex | hip and ridge cap | 8 | 30 | 20 |
| Owens Corning DecoRidge | hip and ridge cap | 8 | 30 | 20 |
| CertainTeed Shadow Ridge | hip and ridge cap | 8 | 30 | 20 |
| GAF Pro-Start | starter strip | — | — | about 120 |
| CertainTeed SwiftStart | starter strip | — | 18 | 116 |
| Owens Corning Starter Strip Plus | starter strip | — | 32 | 105 |
| CertainTeed Starter, 10 x 36 in | starter strip | — | 34 | 102 |
| 3-tab shingles with the tabs cut off (26 per bundle) | starter strip | — | 26 | 78 |
Cutting 3-tab shingles for cap and starter, and why laminated shingles cannot be
A 12 x 36 in 3-tab shingle cut at the two cutouts gives three 12 in caps; laid at a 5 in exposure, a 26-shingle bundle covers 26 × 3 × 5 ÷ 12 = 32.5 lin ft, and the tool rounds that to 33. A 3-tab shingle with its tabs cut off is a 3 ft starter, so a bundle gives 78 ft. The same shingle as a cap for a laminated roof is a mismatch in thickness, color and warranty; the makers' bulletins say only 3-tab shingles may be cut for starter or cap, and that a laminated shingle cut for cap is not covered. A laminated shingle has two layers with the adhesive in a different place, it will not bend over a ridge in one piece, and the two layers do not bend together. For a laminated roof use the cap product the maker lists; at 100 ft of ridge, 33 ft caps take 4 bundles and 8 in exposure caps take 5.
Drip edge under IRC R905.2.8.5
The drip edge rule is short: "A drip edge shall be provided at eaves and rake edges of shingle roofs." Pieces are lapped not less than 2 in, so a 10 ft length covers 9.83 ft, and the tool divides the eave and rake total by that: 140 ft is 15 pieces, where dividing by a full 10 ft would give 14. The same section sets the drip edge not less than ¼ in below the sheathing and 2 in back onto the deck, fastened at not more than 12 in on center, with the underlayment over the drip edge at the eaves and under it at the rakes.
Underlayment and ice barrier rolls under the shingles
Underlayment is rated by the roll, and the tool divides the measured squares by the squares per roll: 13.4 squares takes 2 synthetic rolls, 4 rolls of #15 felt or 7 rolls of #30. The roll figures are gross; a 432 sq ft roll of #15 lapped 2 in covers about 408 sq ft, which is why the trade calls it 4 squares and not 4.3. The shingle waste is not applied to underlayment.
| Underlayment | Roll | Gross coverage | Squares per roll | Standard and products |
|---|---|---|---|---|
| #15 asphalt felt | 36 in x 144 ft | 432 sq ft | 4 | ASTM D226 Type I or D4869; sold as 4 squares |
| #30 asphalt felt | 36 in x 72 ft | 216 sq ft | 2 | ASTM D226 Type II; sold as 2 squares |
| Synthetic, 48 in roll | 48 in x 250 ft | 1,000 sq ft excluding laps | 10 | ASTM D226 Type II, D4869 Type IV or D8257; GAF FeltBuster, Deck-Armor, Tiger Paw; Titanium UDL |
| Synthetic, 42 in roll | 42 in x 286 ft | 929 sq ft with 3 in laps | 10 (sold as 10 squares) | Owens Corning ProArmor |
| Ice barrier, 2-square roll | 36 in x 66.7 ft | 200 sq ft | not in the tool | ASTM D1970; GAF WeatherWatch and StormGuard, Owens Corning WeatherLock G |
| Ice barrier, 1½ and 1-square rolls | 36 in x 50 ft, 36 in x 33.3 ft | 150 and 100 sq ft | not in the tool | ASTM D1970 |
| Ice barrier, 2¼-square roll | 36 in x 75 ft | 225 sq ft | not in the tool | Grace Ice and Water Shield |
Two layers from 2/12 up to 4/12
IRC R905.2.2 says: "Asphalt shingles shall be used only on roof slopes of 2 units vertical in 12 units horizontal (17-percent slope) or greater." From 2/12 up to 4/12 it adds that "double underlayment application is required in accordance with Section R905.1.1." Table R905.1.1(2) spells the two layers out for asphalt shingles: "apply a 19-inch strip of underlayment felt parallel to and starting at the eaves. Starting at the eave, apply 36-inch-wide sheets of underlayment, overlapping successive sheets 19 inches." At 4/12 and steeper it is one layer, "applied shingle fashion, parallel to and starting from the eave and lapped 2 inches," with end laps of 4 in offset by 6 ft. The tool reads the pitch and doubles the roll count on its own: the same 40 x 30 ft footprint at 3/12 is 1,236.9 sq ft and 12.4 squares, and needs 3 synthetic rolls instead of 2 at 4/12, with the warning printed above the rows. The 2021 code moved the lap rules into that table; R905.2.7 now reads only "Where required, ice barriers shall comply with Section R905.1.2."
Ice barrier at the eaves
R905.1.2 requires an ice barrier "in areas where there has been a history of ice forming along the eaves causing a backup of water as designated in Table R301.2," running from the lowest edge of the roof "to a point not less than 24 inches (610 mm) inside the exterior wall line of the building," and on slopes of 8/12 and steeper "not less than 36 inches (914 mm) measured along the roof slope from the eave edge." Detached accessory structures without conditioned floor area are excepted. Whether your county is designated is a Table R301.2 entry your building department fills in, so the tool does not count ice barrier; measure the eave length, work out the width the rule gives for your overhang and wall thickness, and buy by the 200 sq ft roll from the table.
Roofing nails per square of shingles
Nails are counted from pieces, not from squares, because the pieces per square vary by product. IRC R905.2.6 sets the floor: shingles get the fasteners the maker's instructions call for, "but not less than four fasteners per strip shingle or two fasteners per individual shingle." At four nails, a square of 3-tab takes 320 and a square of laminated shingles 256, which is the figure one maker prints as nails per square. R905.2.5 sets the nail: a minimum 12-gauge shank with a ⅜ in head, long enough to go not less than ¾ in into the sheathing, or through it where the sheathing is thinner than ¾ in.
| Shingle | Pieces per square | Nails per square at 4 | Nails per square at 6 |
|---|---|---|---|
| 3-tab, 12 x 36 in | 80 | 320 | 480 |
| Architectural, laminated | 64 | 256 | 384 |
| Heavyweight, 4 bundles per square | 56 | 224 | 336 |
| Premium shake-look, 5 bundles per square | 90 | 360 | 540 |
Four nails or six
Six nails is the high-wind and steep-slope pattern, and some wind warranties depend on it: one maker's laminated sheets carry the higher wind rating "only with 6-nail application." Above 21/12 the IRC hands the attachment to the maker's instructions. Pick 6 in the tool and the default roof goes from 3,780 nails to 5,670. Coil roofing nails are sold 7,200 to a box, so either figure is one box; a 60 x 30 ft roof at 8/12 needs 6,092, still one box at 4 per shingle. Nail length depends on the deck and on whether old shingles stay under the new ones; the wrapper gives it.
Worked shingle estimates: gable, hip, garage and area-only
Each row is one run of the calculator with the inputs named in the first column, so the table doubles as a check on the tool. Synthetic underlayment and 4 nails per shingle throughout; the last column is bundles of cap at 33 lin ft, bundles of pre-cut starter at 100 lin ft and pieces of drip edge, where lengths were entered.
| Roof and inputs | Area | Sq | To buy | Bundles | Pieces | Nails | Rolls | Cap / starter / drip |
|---|---|---|---|---|---|---|---|---|
| Gable, 40 x 28 ft footprint at 6/12, architectural, 10%; 40 ft ridge, 142 ft of eave and rake | 1,252.2 sq ft | 12.5 | 13.8 | 42 | 882 | 3,528 | 2 | 2 / 2 / 15 |
| Hip, 50 x 36 ft footprint at 6/12, architectural, 15%; 86 ft of ridge and hips, 172 ft of eave | 2,012.5 sq ft | 20.1 | 23.1 | 70 | 1,482 | 5,928 | 3 | 3 / 2 / 18 |
| Garage, 24 x 24 ft with 1 ft overhangs (26 x 26 footprint) at 4/12, 3-tab, 10% | 712.6 sq ft | 7.1 | 7.8 | 24 | 628 | 2,512 | 1 | — |
| Ranch, 60 x 30 ft footprint at 8/12, architectural, 10% | 2,163.3 sq ft | 21.6 | 23.8 | 72 | 1,523 | 6,092 | 3 | — |
| Area entered directly, 2,000 sq ft, architectural, 10% | 2,000 sq ft | 20 | 22 | 66 | 1,408 | 5,632 | 2 | — |
The garage row is the one most people get wrong. A 24 x 24 ft building is 576 sq ft of floor, but the roof covers 26 x 26 ft with its overhangs, and at 4/12 that is 712.6 sq ft: a materials list written for 600 sq ft is short before the starter and cap are counted. The hip row shows why the waste setting matters more than the roof type: the area is the same arithmetic as a gable, and the 15% is what pays for the diagonal cuts. The 2,000 sq ft row is the question asked from a measured area or a report; at 10% it is 66 bundles; 3-tab on the same area is the same 66 bundles but 1,760 pieces. For 1,500 and 3,000 sq ft the tool gives 50 and 99 bundles.
What the IRC says about asphalt shingles, and what it leaves to the wrapper
Section R905.2 of the 2021 International Residential Code covers asphalt shingles; the underlayment rules moved into Section R905.1.1 and its three tables in this edition. The values below are read from the Seattle SDCI 2021 Chapter 9 reprint of the code, pages 9-2 to 9-7, where none of these sections carries a Washington or Seattle amendment mark. The code sets slopes, layers, fasteners and edges; it sets no bundles per square, no exposure and no waste, which is why those come from the product sheets on this page.
| Rule | Value | IRC 2021 section |
|---|---|---|
| Minimum slope for asphalt shingles | 2 units vertical in 12 units horizontal (17-percent slope) | R905.2.2 |
| Underlayment from 2/12 up to 4/12 | two layers: a 19 in strip at the eave, then 36 in sheets lapped 19 in | R905.2.2; Table R905.1.1(2) |
| Underlayment at 4/12 and steeper | one layer, shingle fashion, lapped 2 in; end laps 4 in offset 6 ft | Table R905.1.1(2) |
| Underlayment type | ASTM D226 Type I or II, D4869, D6757; D226 Type II or D4869 Type III or IV where wind design is required | Table R905.1.1(1) |
| Ice barrier | where Table R301.2 designates it: two cemented layers or a self-adhering sheet, to 24 in inside the exterior wall line; 36 in along the slope on 8/12 and steeper | R905.1.2 |
| Deck | solidly sheathed | R905.2.1 |
| Shingle standard | ASTM D3462 | R905.2.4 |
| Wind resistance | tested to ASTM D7158, class D, G or H by the ultimate design wind speed in Table R905.2.4.1; D3161 class A, D or F for shingles outside D7158 | R905.2.4.1 |
| Fasteners | minimum 12-gauge shank, ⅜ in head, ASTM F1667; not less than ¾ in into the sheathing, or through sheathing thinner than ¾ in | R905.2.5 |
| Fasteners per shingle | the maker's instructions, but not less than four per strip shingle or two per individual shingle; above 21/12 per the maker's instructions | R905.2.6 |
| Drip edge | at eaves and rakes; laps not less than 2 in; ¼ in below the sheathing and 2 in onto the deck; fastened at not more than 12 in on center | R905.2.8.5 |
| Flashing | base and cap flashing, valleys, sidewalls per the section and the maker's instructions | R905.2.8 |
The slope rule is the one the tool enforces. At flat or 1/12 it prints that asphalt shingles are not permitted and points to the low-slope coverings in R905.1.1; a lapped metal panel roof can go to 3/12 without lap sealant, and standing seam lower still, which is the metal roofing panel calculator (planned). From 2/12 up to 4/12 it doubles the underlayment. Everything else in the table is a check against your plans and your building department, not something the calculator can decide; the site's reading of code sources is set out on the methodology page.
Eight ways a shingle estimate goes wrong
Each row is a mistake that appears on calculator pages and in roofing questions, with the arithmetic that catches it.
| Mistake | Wrong | Right |
|---|---|---|
| Floor area or footprint used as roof area | 24 x 24 ft garage, buy for 600 sq ft | 26 x 26 ft with overhangs at 4/12 is 712.6 sq ft |
| Three bundles per square assumed for every shingle | 140 bundles for 46 squares of a 4-bundle shingle | the wrapper says 4 or 5; 46 squares is 184 bundles at 4 |
| Bundle mistaken for a square | a 3-tab bundle covers 100 sq ft | a bundle covers about a third of a square, 33 sq ft |
| Squares rounded before multiplying | 16.2 squares, call it 17, times 3 = 51 bundles | 16.2 × 3 = 48.6, 49 bundles; round once, at the end |
| Starter and cap left out, or cut from laminated shingles | field bundles only; cap cut from the leftover laminates | starter by eave and rake length, cap by ridge and hip length, from 3-tab or a cap product |
| Waste counted twice, or not at all | 15% added to a to-buy figure that already had it | add waste once to the measured squares; the tool prints both |
| Nails counted per bundle at the per-square figure | 320 nails per bundle | 320 per square of 3-tab, about 107 per bundle; 256 per square of laminates |
| Underlayment at the shingle waste, or one layer under 4/12 | 2 rolls plus 10% | rolls from measured squares; two layers from 2/12 up to 4/12 |
Which roofing calculator do you need?
This page counts the material for a shingle roof. The measuring method behind the footprint, with the planes, valleys and dormers worked one at a time, is in how to measure a roof for shingles; squares as a unit are explained in roof square footage and roofing squares; pitch by hand is in how to calculate roof pitch. The tools below are planned and not yet live where marked.
| Job | Use | What it adds |
|---|---|---|
| Roof surface area, squares and overhang from any shape | Roof area calculator (planned) | plan area, slope factor, squares and the roofing-square definition |
| Pitch from a rise and run, or from an angle | Roof pitch calculator (planned) | rise in 12, degrees, percent and the slope factor |
| Every pitch as an angle | Roof pitch to degrees chart (planned) | the full table and a converter |
| Hip roof planes and hip length | Hip roof area calculator (planned) | the same area as a gable, worked both ways, plus the hip rafter factor |
| Rafter length for the pitch | Rafter length calculator (planned) | common rafter length, overhang and plumb cut |
| Metal panels instead of shingles | Metal roofing panel calculator (planned) | panels, screws and closures, with the lower slope limits |
| Trusses for a new roof | Roof truss calculator (planned) | truss count and spacing |
| Sheathing under the shingles | Plywood and OSB sheet calculator (planned) | 4 x 8 sheets for the roof deck, which also checks the bundle count |
| Siding for the gable ends | Siding calculator (planned) | squares of siding by exposure |
| Every roofing tool | Roofing calculators hub (planned) | all roofing calculators on the site |
Shingle calculator FAQ
How many bundles of shingles do I need?
Roof area times the slope factor, divided by 100, times the waste, times the bundles per square, rounded up: the default 40 x 30 ft roof at 6/12 is 45 bundles. The measuring method, plane by plane, is in how to measure a roof for shingles.
How many bundles of shingles are in a square?
Three for 3-tab and standard architectural shingles, four for heavyweight designer shingles and five for premium shake-look shingles. A square is 100 sq ft of roof surface. The data sheets for the common laminated shingles and the 12 x 36 in 3-tabs all print 3 bundles per square; the heavier lines print 4 or 5, and some do not print the figure at all, in which case the wrapper is the only source. One common error is dividing a delivery by the wrong number: 182 bundles of a 3-bundle shingle is 60 squares, not 45. The bundles-per-square figure for a cap or starter product is different again, because those are bought by length.
How many shingles are in a bundle?
About 26 for a 12 x 36 in 3-tab and 20 to 22 for a laminated shingle, which is why the sheets give pieces per square rather than per bundle: 80 for the 3-tab, 64 to 66 for most laminates, 60 for the larger IKO format, 56 for the 14 x 42 in Atlas shingle, 90 for a premium shake-look shingle at a 4 in exposure. The 29-per-bundle figure that circulates is from an older 3-tab count. Bundles of the same product can hold different counts: one maker packs a sales square as 20 + 22 + 22. The calculator works from pieces per square, so the bundle count does not matter to it; it matters when you count a delivery.
How many square feet does a bundle of shingles cover?
About 33 sq ft for a 3-bundle shingle, 32.8 where the three bundles are rated at 98.4 sq ft, 25 at four per square and 20 at five. The whole relationship between bundles, squares and coverage is in shingle bundles, squares and coverage.
Do I use the square footage of the house or the roof?
The roof, and the roof is bigger than the house. House square footage is floor area, counted on every story, and a two-story house of 2,000 sq ft covers about 1,000 sq ft of ground. The roof covers that footprint plus the overhangs, and its surface is the footprint stretched by the slope factor, 1.118 at 6/12 and 1.414 at 12/12. A 1,700 sq ft house can carry 4,700 sq ft of roof. Measure the footprint eave to eave and rake to rake, overhangs in, enter it with the pitch, and the tool does the stretching; or measure the planes and enter the surface area directly.
Does the shingle calculator include waste, and how much should a hip roof add?
Yes, the default is 10%, printed under the result, and it is applied to the shingles, pieces and nails only. A hip roof has the same surface area as a gable over the same footprint at the same pitch, so the extra is all waste from the diagonal cuts along the hips: 15% is the usual figure, 20% for a cut-up roof with several hips, valleys and dormers. On the default roof that is 47 bundles at 15% and 49 at 20% against 45 at 10%. Underlayment, cap, starter and drip edge are not inflated by the waste, because they are counted from their own lengths and roll ratings.
Can I cut architectural shingles for ridge cap, and how many bundles of cap do I need?
No. Laminated shingles are two layers with the adhesive in a different place; they will not bend over a ridge in one piece, and the makers' bulletins say that a laminated shingle cut for cap is not covered by the warranty. Cap for a laminated roof is a cap product, 20 to 33 lin ft per bundle by exposure, or 3-tab shingles cut at the cutouts for a 3-tab roof, 32.5 ft per 26-shingle bundle. Divide the total ridge and hip length by the figure for your product and round up: 40 ft of ridge is 2 bundles at 33 ft or at 20 ft, and 100 ft is 4 at 33 ft and 5 at 20 ft.
How much starter strip do I need?
One bundle for every 100 to 120 ft of eave and rake, depending on the product: pre-cut starter bundles are labelled 102, 105, 116 and about 120 lin ft, and 3-tab shingles with the tabs cut off give 3 ft each, 78 ft per bundle. Measure every eave, and the rakes too unless the maker's instructions say eaves only; a maker's warranty may require starter on both. Enter the total in the tool and it divides by the coverage you pick: 140 ft is 2 bundles of pre-cut starter at the 100 ft nominal, and 2 bundles of cut 3-tab. A whole 3-tab shingle laid upside down as starter puts the seal strip in the wrong place and is not an accepted method.
How many rolls of underlayment per square, and when does it need two layers?
A synthetic roll covers 10 squares, a roll of #15 felt 4 squares and a roll of #30 felt 2 squares, gross; the tool divides the measured squares by those and rounds up, so the default roof takes 2 synthetic rolls, 4 of #15 or 7 of #30. Two layers are required under asphalt shingles from 2/12 up to 4/12, by IRC R905.2.2 and Table R905.1.1(2): a 19 in strip at the eave, then 36 in sheets lapped 19 in. The tool reads the pitch and doubles the roll count on those slopes, with a warning. At 4/12 and steeper it is one layer lapped 2 in. Ice barrier at the eaves is a separate self-adhering product and is not counted.
How many nails per square of shingles?
320 for 3-tab and 256 for laminated shingles at four nails per shingle, the IRC R905.2.6 minimum, or 480 and 384 at six. The count comes from the pieces per square, which is why heavyweight shingles take fewer nails per square (224 at four) and premium shake-look shingles more (360). The default roof takes 3,780 nails at four per shingle and 5,670 at six, both inside one 7,200-nail box of coil nails. Six nails is the high-wind and steep-slope pattern and some wind warranties depend on it. R905.2.5 sets the nail itself: 12-gauge shank, ⅜ in head, ¾ in into the deck or through thin sheathing.
What is the minimum roof pitch for asphalt shingles?
2/12. IRC R905.2.2 allows asphalt shingles only on slopes of 2 units vertical in 12 units horizontal or greater, and from 2/12 up to 4/12 it requires two layers of underlayment applied as Table R905.1.1(2) describes. The calculator refuses flat and 1/12 with a warning that names the section and points to the low-slope coverings in R905.1.1, and it doubles the underlayment from 2/12 to 4/12. Below 2/12 the choices are a membrane, roll roofing or a metal system with sealed laps; lapped metal panels are allowed down to 3/12 without lap sealant and lower with it under R905.10.1.1, which the metal roofing panel calculator (planned) works to.
How much does a bundle of shingles weigh, and how many are on a pallet?
A square of laminated shingles is 217 to 240 lb on the CertainTeed Landmark sheets, so a bundle is about 72 to 80 lb; 3-tab bundles run lighter, premium shake-look shingles are 350 to 468 lb per square and come 4 or 5 bundles to it. Pallet counts are not standard: suppliers quote 21 to 42 bundles per pallet depending on the product and the yard, so ask when you order and plan where a pallet will stand. For a tear-off, weight per square of the old roof is what the disposal is figured on, and a roof with a second layer under the top one weighs about twice what the top layer suggests.
How do I measure a roof for shingles?
Footprint eave to eave and rake to rake with the overhangs, plus the pitch, for a gable; each plane as a rectangle or triangle for anything else, added up as surface area. The full method, with valleys and dormers, is in how to measure a roof for shingles.
How many bundles for a 1,500, 2,000 or 3,000 sq ft roof?
50, 66 and 99 bundles of a 3-bundle shingle at 10% waste, if those are roof surface areas: 1,500 sq ft is 15 squares, 16.5 to buy; 2,000 is 20 squares, 22 to buy; 3,000 is 30 squares, 33 to buy. If the figure is the house or the footprint, it has to be stretched by the slope factor first; 2,000 sq ft of footprint at 6/12 is 2,236 sq ft of roof. Use the area setting of the tool for a measured surface, and the footprint setting with the pitch for a ground measurement. At 15% waste the 2,000 sq ft roof is 69 bundles; as 3-tab it is the same 66 bundles but 1,760 pieces.
Why do three bundles cover 98.4 sq ft and not 100?
Because coverage is pieces times exposed area, and 64 laminated shingles of 39⅜ in at a 5⅝ in exposure come to 98.4 sq ft, which is what the Owens Corning and TAMKO sheets print. A 12 x 36 in 3-tab at 5 in covers exactly 100 per 80 pieces, and one maker packs 60 larger shingles so that three bundles reach 100. The trade orders in squares and the calculator does the same, treating a 98.4 sq ft square as a square; the 1.6% is inside any waste allowance, and on a 20-square roof it is 32 sq ft, one bundle. If you want it counted, raise the waste by 2 points.
Should I buy extra bundles for repairs later?
One bundle beyond the waste is a reasonable keep, no more. Shingles stored outdoors fuse and the seal strip degrades, so old bundles are rarely usable years later, and unopened bundles can usually be returned to the yard. The reason to keep one is color: shingles are made in lots, and a repair from the same lot matches where a new bundle of the same color name may not. Check the lot numbers on the wrappers when the delivery arrives, before the roof goes on, and keep the spare from the same lot. The waste allowance already covers damaged pieces on the job.
Source and verification of these shingle figures
Every square, bundle, piece, nail and roll count on this page is regenerated from the arithmetic the calculator runs and checked by script against both the copy and the figures the tool displays at the same inputs; if a number here disagrees with the tool, that is a fault to report through the contact page. Bundles, pieces, exposure, sizes and the cap and starter coverages are read from the manufacturers' published data sheets and spec pages named in the tables; the wrapper on the product you buy governs. Sections R905.1.1, R905.1.2, R905.2 to R905.2.8.5 and Tables R905.1.1(1) to (3) were read from the 2021 Seattle Residential Code, Chapter 9, pages 9-2 to 9-7, which reproduces the 2021 IRC with Washington and Seattle amendments marked; none of the sections used here carries one. Waste figures are labelled by who gives them. How sources are chosen and checked is set out in the methodology.