A square is 100 square feet of roof. A square of shingles may not cover one.
Steep-slope roofs · U.S. customary units · reference
The unit is simple. Almost nothing that gets counted in it is.
What is a roofing square, and why does my number never match the contractor’s?
A roofing square is 100 square feet of roof surface — a unit of area, not a product. Contractors quote in squares because materials are packaged and specified that way. Your number differs from theirs because they measure sloped surface, not floor footprint, add waste, and count a bundled square that may cover only 98.4 square feet.
The unit, and the numbers people confuse with itSection link
A square is a unit of area. Bundles per square and coverage per square are separate published numbers, and they move independently of each other.
- One roofing square
- 100 sq ft of roof surfaceA 10 ft × 10 ft patch measured on the slope, not on the ground and not on a floor plan.
- Bundles in one square
- 3 to 6Three for many asphalt laminates, four for others, four for cedar shingles, five for 18-inch cedar shakes in a 12/12 pack, and six for Owens Corning’s heavy shake-profile laminates.
- What one packaged square covers
- 98.4 to 100.0 sq ftOwens Corning’s own guide specification publishes 98.4 sq ft for its Duration laminates, 99.5 for Berkshire, and 100.0 for Supreme — three figures, one manufacturer, one document.
- Waste allowance
- Applied once, to the orderIt changes how much material is bought. It never changes how much roof was measured.
- What squares do not cover
- Starter, ridge, valley, edgesThose are bought by the linear foot of eave, rake, hip, and ridge — quantities the square count cannot tell you.
| Measured roof surface | Squares | 3 bundles per square, 100.0 sq ft coverage | 3 bundles per square, 98.4 sq ft coverage | 4 bundles per square, 98.4 sq ft coverage |
|---|---|---|---|---|
| 500 sq ft | 5.0 | 15 | 16 | 21 |
| 1,000 sq ft | 10.0 | 30 | 31 | 41 |
| 1,500 sq ft | 15.0 | 45 | 46 | 61 |
| 2,000 sq ft | 20.0 | 60 | 61 | 82 |
| 2,500 sq ft | 25.0 | 75 | 77 | 102 |
| 3,000 sq ft | 30.0 | 90 | 92 | 122 |
| 3,500 sq ft | 35.0 | 105 | 107 | 143 |
| 4,000 sq ft | 40.0 | 120 | 122 | 163 |
Read this table one item at a time
500 sq ft
- Squares
- 5.0
- 3 bundles per square, 100.0 sq ft coverage
- 15
- 3 bundles per square, 98.4 sq ft coverage
- 16
- 4 bundles per square, 98.4 sq ft coverage
- 21
1,000 sq ft
- Squares
- 10.0
- 3 bundles per square, 100.0 sq ft coverage
- 30
- 3 bundles per square, 98.4 sq ft coverage
- 31
- 4 bundles per square, 98.4 sq ft coverage
- 41
1,500 sq ft
- Squares
- 15.0
- 3 bundles per square, 100.0 sq ft coverage
- 45
- 3 bundles per square, 98.4 sq ft coverage
- 46
- 4 bundles per square, 98.4 sq ft coverage
- 61
2,000 sq ft
- Squares
- 20.0
- 3 bundles per square, 100.0 sq ft coverage
- 60
- 3 bundles per square, 98.4 sq ft coverage
- 61
- 4 bundles per square, 98.4 sq ft coverage
- 82
2,500 sq ft
- Squares
- 25.0
- 3 bundles per square, 100.0 sq ft coverage
- 75
- 3 bundles per square, 98.4 sq ft coverage
- 77
- 4 bundles per square, 98.4 sq ft coverage
- 102
3,000 sq ft
- Squares
- 30.0
- 3 bundles per square, 100.0 sq ft coverage
- 90
- 3 bundles per square, 98.4 sq ft coverage
- 92
- 4 bundles per square, 98.4 sq ft coverage
- 122
3,500 sq ft
- Squares
- 35.0
- 3 bundles per square, 100.0 sq ft coverage
- 105
- 3 bundles per square, 98.4 sq ft coverage
- 107
- 4 bundles per square, 98.4 sq ft coverage
- 143
4,000 sq ft
- Squares
- 40.0
- 3 bundles per square, 100.0 sq ft coverage
- 120
- 3 bundles per square, 98.4 sq ft coverage
- 122
- 4 bundles per square, 98.4 sq ft coverage
- 163
Squares are the measured roof surface divided by 100. Bundle counts are rounded up, because bundles are not sold in fractions. The two three-bundle columns differ only in the coverage the manufacturer publishes for that product: at 4,000 square feet, that difference is two extra bundles. To convert the other way, multiply squares by 100 — a 24.5-square roof is 2,450 square feet of surface.
When the square is the right unit to argue inSection link
The square is a good unit for comparing steep-slope proposals for the same scope on the same building. It is a poor unit for almost everything else.
Best when
- You are comparing two or more steep-slope proposals for the same roof and want a unit price you can hold side by side.
- You are sizing an order and need to convert measured area into whole bundles, rolls, and pieces.
- You are sanity-checking whether a quoted quantity is plausible for the building you can see from the driveway.
- You are reading a manufacturer’s data sheet, which publishes coverage, weight, and piece counts per square.
Think twice if
- The work is low-slope or commercial membrane. Those proposals are commonly written per square foot, and mixing the two units silently changes every number by a factor of 100.
- The job is a repair. Repair pricing is driven by trip, access, diagnosis, and detail work, not by area, so a price per square is close to meaningless.
- The roof’s cost is driven by complexity rather than area — many planes, dormers, valleys, penetrations, or steep pitch. Two roofs of identical square count can be very different jobs.
- The proposals state different square counts. Until you know whether each count is measured surface or waste-inclusive order area, dividing by it produces a fake comparison.
- You are estimating from a listing’s living area. Floor area is not footprint, and a two-story house has roughly half the footprint of its living area.
What changes the answer
- Whether the square count on the document is measured roof surface or measured surface plus a waste allowance.
- The waste percentage the estimator used, and whether it was applied to every plane or only to the cut-heavy ones.
- Pitch, which sets the multiplier between footprint and surface — and on wood roofs also caps the exposure, which changes how far a bundle goes.
- The specific product: its bundles per square, its published coverage per square, and whether its accessories are inside the unit price or on separate lines.
- How many tear-off layers, and how much deck replacement, sit inside the per-square number.
Three different areas get called “the roof”Section link
Almost every disagreement about square count is one of these three areas being compared with a different one.
A roofing square is 100 square feet of roof surface. That is the whole definition. It is a unit of area, in the same way an acre is — it names a quantity of surface, and it says nothing about what is on that surface or how much of it comes in a package.
The confusion starts because three different areas all get called the roof, and each of them produces a different square count.
1. The footprint
The footprint, which the glossary calls plan area, is the area of the building measured flat to the outside of the eaves: what you would get by tracing the roof’s outline on the ground. It is the number a satellite image or a plan set gives you first, and it is the number almost every homeowner divides by 100. It is not the roof. A 6:12 roof over a 1,800 square foot footprint has 2,012 square feet of surface, because the rafter is longer than its horizontal run.
Living area is a further step removed. A two-story house with 2,400 square feet of living space may sit on a 1,200 square foot footprint; a sprawling single-story house with the same living area has twice that footprint and roughly twice the roof.
2. The roof surface
The roof surface is the actual sloped area of every plane. It is what a square measures, and it is the number a takeoff produces plane by plane. For a single uniform pitch it is the footprint multiplied by a pitch factor — √(1 + (rise ÷ 12)²), which is 1.118 at 6:12. That multiplier is geometry, not an estimate, but it only applies where the pitch is genuinely uniform. Dormers, a second pitch, porch roofs, and detached structures are separate planes that get measured separately and added.
3. The order area
The order area is the roof surface plus a waste allowance — the extra material consumed by starter cuts, rake cuts, valley cuts, hip and ridge cuts, breakage, and the offcuts that end up in the dumpster. It is a real cost and it belongs in a proposal. It is not roof. Nothing about adding waste changes how much roof was measured, and that distinction is the source of more quote confusion than any other single thing on this page.
We do not publish a waste percentage here, because there is not one to publish. The right allowance depends on the number of planes, the length of valleys and hips relative to field area, the valley method, the shingle’s exposure and cut pattern, and how the crew stages the roof. A simple gable with two planes and no valleys wastes very little. A complex hip roof with four valleys and six penetrations wastes a great deal. Ask what the estimator used and why; the answer tells you something about the estimator.
Why contractors adopted the unit anyway
Because the material is specified, packaged, and sold in it. Manufacturers publish “bundles per square” and “coverage per square” for every shingle. Underlayment is sold the same way: Owens Corning’s guide specification lists its reinforced felt at “Coverage Per Roll: 4 roof squares” and its synthetic underlayment at “5 and 10 roof squares”. A mineral surface roll is listed at “Rolls per Square: 1.” When the inventory, the data sheet, and the delivery ticket are all denominated in squares, the estimate and the price get built in squares too.
The exception is everything that runs along an edge. Starter comes in strips — Owens Corning lists one at “7-1/5 in tall by 33-2/5 ft wide” — and hip and ridge caps come as pieces with a stated exposure. Those are bought by the linear foot of eave, rake, hip, and ridge, and the square count tells you nothing about them.
That matters more than it sounds. Two 6:12 gable roofs over the identical 1,800 square foot footprint are both 20.1 squares. But a 30 ft × 60 ft plan has 120 feet of eave and 67 feet of rake, while a nearly square 42.4 ft × 42.4 ft plan has 85 feet of eave and 95 feet of rake. Same squares. 41% more eave on one of them — and the drip edge, starter course, gutter, and ice barrier all hang off that number, not off the square count.
One square of product does not always cover one square of roofSection link
“Bundles per square” and “coverage per square” are two separate numbers on every data sheet, and neither is a constant.
The trap in the word “square” is that it names both a quantity of roof and a quantity of product, and the two are not equal. A packaged square is whatever the manufacturer decided to call a square. What it actually covers on the roof is published separately, and on the Owens Corning, CertainTeed, and GAF laminates in the table below, that figure is 98.4 square feet, not 100.
Where does 98.4 come from? Arithmetic, not tradition. A metric shingle 39⅜ inches long, installed at 5⅝ inches of exposure, covers 221.5 square inches — 1.538 square feet. Put 64 of them in a square and you get 98.4 square feet. Put 65 in and you get 100.0. That is the whole difference between Owens Corning’s Duration line and its metric Supreme line. CertainTeed arrives at the same 98.4 by a different route: Landmark is 38¾ inches long rather than 39⅜, so 65 pieces at the same exposure also land on 98.4. IKO gets to 100 with only 60 pieces by making the shingle bigger — Cambridge is 40⅞ inches long and installed at 5⅞ inches of exposure, which is 1.67 square feet each. None of them is wrong. They are different products, and each one prints its own number.
| Product | Bundles in one square | Pieces in one square | Coverage of that square | Published by |
|---|---|---|---|---|
| Owens Corning TruDefinition Duration, 13¼ × 39⅜ in (laminate) | 3 bundles of 20 or 22 | 64 | 98.4 sq ft | Owens Corning guide spec 073113 |
| Owens Corning Duration Premium, 13¼ × 39⅜ in (laminate) | 4 bundles of 16 | 64 | 98.4 sq ft | Same document |
| Owens Corning Supreme, 12 × 36 in (three-tab) | 3 bundles of 26, 27, 27 | 80 | 100.0 sq ft | Same document |
| Owens Corning Supreme metric, 13¼ × 39⅜ in (three-tab) | 3 bundles of 21, 22, 22 | 65 | 100.0 sq ft | Same document |
| CertainTeed Landmark, 13¼ × 38¾ in (laminate) | 3 | 65 | 98.4 sq ft | CertainTeed technical data sheet |
| GAF Timberline HDZ, 13¼ × 39⅜ in (laminate) | 3 | 64 | Not printed on the spec sheet; 64 pieces at 39⅜ in × 5⅝ in exposure works out to 98.4 sq ft | GAF spec sheet RESGN467HDZ |
| IKO Cambridge, 13¾ × 40⅞ in (laminate) | 3 bundles of 20 | 60 | 100 sq ft (33.3 sq ft per bundle) | IKO technical data sheet |
| 16-inch No. 1 cedar shingle at 5-inch exposure | 4 | — | 100 sq ft | Cedar Shake & Shingle Bureau |
| The same cedar shingle at 4-inch exposure | 4 | — | 80 sq ft | Cedar Shake & Shingle Bureau |
| 18-inch cedar shake, 12/12 pack, 7½-inch exposure | 5 | — | 100 sq ft | Cedar Shake & Shingle Bureau |
| The same shake in a 9/9 pack | 5 | — | 75 sq ft | Cedar Shake & Shingle Bureau |
Read this table one item at a time
Owens Corning TruDefinition Duration, 13¼ × 39⅜ in (laminate)
- Bundles in one square
- 3 bundles of 20 or 22
- Pieces in one square
- 64
- Coverage of that square
- 98.4 sq ft
- Published by
- Owens Corning guide spec 073113
Owens Corning Duration Premium, 13¼ × 39⅜ in (laminate)
- Bundles in one square
- 4 bundles of 16
- Pieces in one square
- 64
- Coverage of that square
- 98.4 sq ft
- Published by
- Same document
Owens Corning Supreme, 12 × 36 in (three-tab)
- Bundles in one square
- 3 bundles of 26, 27, 27
- Pieces in one square
- 80
- Coverage of that square
- 100.0 sq ft
- Published by
- Same document
Owens Corning Supreme metric, 13¼ × 39⅜ in (three-tab)
- Bundles in one square
- 3 bundles of 21, 22, 22
- Pieces in one square
- 65
- Coverage of that square
- 100.0 sq ft
- Published by
- Same document
CertainTeed Landmark, 13¼ × 38¾ in (laminate)
- Bundles in one square
- 3
- Pieces in one square
- 65
- Coverage of that square
- 98.4 sq ft
- Published by
- CertainTeed technical data sheet
GAF Timberline HDZ, 13¼ × 39⅜ in (laminate)
- Bundles in one square
- 3
- Pieces in one square
- 64
- Coverage of that square
- Not printed on the spec sheet; 64 pieces at 39⅜ in × 5⅝ in exposure works out to 98.4 sq ft
- Published by
- GAF spec sheet RESGN467HDZ
IKO Cambridge, 13¾ × 40⅞ in (laminate)
- Bundles in one square
- 3 bundles of 20
- Pieces in one square
- 60
- Coverage of that square
- 100 sq ft (33.3 sq ft per bundle)
- Published by
- IKO technical data sheet
16-inch No. 1 cedar shingle at 5-inch exposure
- Bundles in one square
- 4
- Pieces in one square
- —
- Coverage of that square
- 100 sq ft
- Published by
- Cedar Shake & Shingle Bureau
The same cedar shingle at 4-inch exposure
- Bundles in one square
- 4
- Pieces in one square
- —
- Coverage of that square
- 80 sq ft
- Published by
- Cedar Shake & Shingle Bureau
18-inch cedar shake, 12/12 pack, 7½-inch exposure
- Bundles in one square
- 5
- Pieces in one square
- —
- Coverage of that square
- 100 sq ft
- Published by
- Cedar Shake & Shingle Bureau
The same shake in a 9/9 pack
- Bundles in one square
- 5
- Pieces in one square
- —
- Coverage of that square
- 75 sq ft
- Published by
- Cedar Shake & Shingle Bureau
Every figure here is the manufacturer’s or the bureau’s own published number for that named product. None of it is an average and none of it is a rule. Notice that the last four rows change coverage without changing the packaging at all: on a wood roof, installed exposure is what decides how far a bundle goes, and the roof’s slope is what constrains exposure.
Underlayment is sold in squares too — but not on the same basis
Owens Corning lists its reinforced felt as a 36-inch roll, 141.5 feet long, covering four roof squares. Do the arithmetic on the dimensions and the roll holds 424.5 square feet of material for 400 square feet of coverage. The missing 24.5 square feet — about 5.8% — is close to what a 2-inch head lap on a 36-inch-wide roll consumes. The synthetic underlayment in the same document is 48 inches by 250 feet and listed at ten squares, which is its gross area exactly — so on that product the laps come out of the coverage the buyer thought they had.
The practical consequence is small but real: two rolls listed in the same unit can mean different things, and a takeoff built on listed coverage for one and gross area for the other will be short.
1,800 square feet of footprint, start to bundle countSection link
A simple gable at a uniform 6:12 pitch, ordered in a laminated shingle published at 3 bundles and 98.4 square feet per square. Every step is reproducible with a calculator.
Step 1 — Footprint
1,800 sq ft, measured flat to the outside of the eaves. Overhangs are part of the footprint you start from, because they are part of the roof you are covering.
Step 2 — Roof surface
1800 × 1.118 = 2012.4 sq ft. The multiplier is √(1 + (6 ÷ 12)²). That is 20.1 squares, and it is the only number on this page that is “how big the roof is.”
Step 3 — Order area
2012.4 × 1.1 = 2213.6 sq ft, or 22.1 squares. The 10% is an assumption for this example, not a recommendation. Apply it here, to the order, and apply it exactly once.
Step 4 — Bundles
2213.6 ÷ 98.4 = 22.50 product squares, and 22.50 × 3 = 67.5. Round up: 68 bundles. Dividing by 100 instead of 98.4 would have given 67 — one bundle short, on a roof this size.
Step 5 — Everything the squares did not count
Linear feet of eave, rake, hip, and ridge, for starter, drip edge, ridge cap, and gutter. Underlayment by the roll. Ice barrier where the adopted code and the assembly call for it. Valley material. Flashing at every wall, chimney, and penetration. Fasteners. None of those quantities are derivable from 20.1 squares, and a proposal that lists only squares has not priced them where you can see.
The two ways this goes wrong
Waste applied twice. Take 22.1 squares off a proposal — a number that already contains the allowance — and add 10% again, and you get 24.4 squares and 75 bundles. That is 7 bundles more than the roof needs, roughly 221 square feet of roofing sitting in a driveway.
Slope skipped. Divide the footprint by 100 and you get 18.0 squares and 54 bundles — 14 short, or 21% of the order. This is the error behind most of the gap between a homeowner’s number and a contractor’s, and it gets larger with every step of pitch: the same footprint at 12:12 is 25.5 squares.
Turning a price per square into something comparableSection link
Two proposals for the same roof, at the same total price, can show unit prices nearly ten percent apart. Neither is lying.
| Line | Proposal A | Proposal B |
|---|---|---|
| Total price | $18,000 | $18,000 |
| Squares written on the proposal | 22.1 | 20.1 |
| What that square count is | Measured surface plus a 10% waste allowance | Measured surface only; waste is carried inside the unit price |
| Price ÷ the squares on the proposal | $813 per square | $894 per square |
| Price ÷ measured surface (20.1 squares) | $894 per square | $894 per square |
| Price ÷ square foot of measured surface | $8.94 per sq ft | $8.94 per sq ft |
Read this table one item at a time
Total price
- Proposal A
- $18,000
- Proposal B
- $18,000
Squares written on the proposal
- Proposal A
- 22.1
- Proposal B
- 20.1
What that square count is
- Proposal A
- Measured surface plus a 10% waste allowance
- Proposal B
- Measured surface only; waste is carried inside the unit price
Price ÷ the squares on the proposal
- Proposal A
- $813 per square
- Proposal B
- $894 per square
Price ÷ measured surface (20.1 squares)
- Proposal A
- $894 per square
- Proposal B
- $894 per square
Price ÷ square foot of measured surface
- Proposal A
- $8.94 per sq ft
- Proposal B
- $8.94 per sq ft
The dollar amounts are arbitrary inputs chosen so the division is visible. They are not observations of any market and should not be read as one. What is real here is the arithmetic: dividing by a square count inflated by a 10% waste allowance produces a unit price 9% lower for identical work.
- Units
- U.S. dollars per roofing square (100 sq ft) of measured roof surface
- Scope included
- Whatever the proposal in front of you defines. This page publishes no scope of its own; a normalized unit price is only meaningful between proposals describing the same work.
- Not included
- Everything the proposal excludes. Tear-off layers, deck replacement allowances, underlayment type, ice-barrier extent, flashing replacement, disposal, and permits all sit inside or outside a per-square number depending on how it was written.
- Geography
- None. The dollar figures above are invented inputs chosen to show the arithmetic, not observations of any market or region.
- Data as of
- Not applicable — no market data is used on this page.
- Confidence
- No confidence is claimed for the dollar amounts, because they are not measurements. The arithmetic is exact; the inputs are illustrative.
Proposal A wrote its square count against the order area, because that is what its estimating software prints. Proposal B wrote its square count against the measured surface and carried the waste inside its unit rate, because that is how its estimator was taught. Both are common. Both are defensible. Neither is disclosed unless you ask.
The damage is done at the moment of comparison. Take A’s $813 per square, apply it to B’s 20.1 squares, and you get $16,364 — so B looks about $1,636 more expensive for the same work at the same price. That is not a negotiating insight. It is a unit error.
The fix is one rule: divide by the measured roof surface, never by the square count printed on the document. If the proposal does not say which its number is, that is the first question to ask, and the answer belongs in writing.
Normalizing a unit price makes two numbers comparable. It does not make two proposals comparable. Same unit price, different scope, is a different product at the same headline rate — which is exactly how the cheapest-looking bid usually gets to be the cheapest-looking bid.
What moves the count on a real buildingSection link
- Slope and drainage
Pitch acts twice. It sets the multiplier between footprint and surface, so a steeper roof is more squares over the same ground. On wood roofs it also caps the maximum weather exposure — the amount of each shingle left visible below the one above it — and exposure decides how far a bundle goes.
The Cedar Shake & Shingle Bureau publishes both tables on one page. A four-bundle square of 16-inch shingles covers 100 square feet at 5-inch exposure, 90 at 4½ inches, 80 at 4 inches, and 70 at 3½ inches. The bureau’s own exposure table then permits 5 inches on slopes of 4:12 and steeper for a No. 1 Blue Label 16-inch shingle, but holds that same shingle to 3¾ inches on slopes between 3:12 and 4:12. The bureau does not print a 3¾-inch coverage figure; its neighboring rows are 80 square feet at 4 inches and 70 at 3½. Either way the flatter roof buys something on the order of a third more material for exactly the same area — and no asphalt-shingle intuition predicts that.
Exposure and headlap limits come from the manufacturer’s published instructions and from the code edition your jurisdiction has adopted and amended — there is no national rule. The Cedar Shake & Shingle Bureau prints the instruction on the same page as the tables: check with the building code official for the local jurisdiction.- Structural weight
A square is mass, not an abstraction. CertainTeed publishes Landmark at 211 to 225 pounds per square, which is roughly 70 to 75 pounds per bundle. The 20.1-square example roof is on the order of 4,246 to 4,528 pounds of covering before underlayment, and material staged on a roof arrives as concentrated stacks rather than as spread load.
Whether a deck and frame can carry a second layer of covering, a heavier material, or a staged load is a structural question about one specific building. It is answered by a licensed engineer or the authority having jurisdiction looking at that building — never by a weight-per-square figure on a data sheet.- Access and site conditions
Over-ordering is not free. Extra bundles are delivered, hoisted, staged, and then either returned under whatever the supplier’s restocking policy actually says or left in a garage. Under- ordering costs more: a crew stopping short on the last slope means a return trip, and the replacement bundles may come from a different production run with a visibly different granule blend.
- Code and jurisdiction
This page cites no code provision, because a unit of measure is not a code subject. The things that change your bundle count — exposure, headlap, the number of layers permitted, ice-barrier extent, underlayment type — very much are. Those come from the code edition your jurisdiction has adopted, plus its local amendments, plus the manufacturer’s instructions for the specific product. Model code text is not the law anywhere until a jurisdiction adopts it.
Confirm the adopted edition, the amendments, and how they apply to your assembly with your building department before treating any quantity as settled.- Low-slope and commercial work
Low-slope membrane proposals are commonly written per square foot rather than per square, and the insulation, cover board, and attachment layers are priced separately from the membrane. Before comparing anything, check which unit the document in front of you uses. A per-square figure read as a per-square-foot figure is off by a factor of one hundred, and it is an easy mistake to make when both units appear in the same paragraph.
What the order quantity has to do with the warrantySection link
The fastest way to void the coverage that was paid for is to stretch a short order to fit.
- Warranties are conditioned on the installation instructions
Exposure, headlap, fastener count, and fastener placement are all in the manufacturer’s published instructions, and coverage is conditioned on following them. When an order comes up short, the cheapest field fix is to open the exposure slightly across the remaining courses. It is nearly invisible from the ground for the first few years, it reduces headlap, and it takes the assembly outside the instructions the warranty depends on.
- Fire and wind classes describe an assembly, not a bundle
The listings printed on a shingle data sheet — ASTM E108 and UL 790 Class A for fire, ASTM D3161 Class F and ASTM D7158 Class H for wind — describe a tested roof assembly installed as specified: deck, underlayment, fasteners, and covering together. They are not properties the shingle carries by itself in the bundle, and a marketing wind speed is not a code determination for your building. Changing exposure or fastening to make a short order reach changes the thing that was tested.
- Leftover bundles are stock, not coverage
Material left over from an over-order is repair stock and nothing more. It carries no separate warranty and it does not extend anything.
Repairability
Keep one or two bundles if the job over-ordered, and label them. Record the product name, the color, and the code printed on the bundle wrapper — GAF, for example, tells installers that Timberline HDZ and Timberline HD may be mixed on one roof only when the six-digit codes on the end of the bundle match, and that the older product’s instructions then govern. Years later that label is the difference between a matched repair and a patch you can see from the street.
Store them flat, out of direct sun, off a concrete floor. Granule color blends drift between production runs and plants, so an exact match bought later is not something to count on.
A warranty is a contract between a reader and whoever wrote it. What it covers, what voids it, whether it transfers, and how it is enforced are set by that document and by the law where the reader lives. Read the actual warranty for the product and the installer in front of you — not a summary of one, including this one.
Questions that make a square count checkableSection link
None of these are gotchas. A competent estimator answers all six in under a minute.
Is the square count on this proposal measured roof surface, or does it already include waste?
This is the single question that makes two proposals comparable. A good answer is one word plus a number. An answer that treats the distinction as pedantic tells you the estimate was printed rather than built.
What waste percentage did you use, and did you apply it to every plane or only to the cut-heavy ones?
There is no correct percentage, so you are not checking the number — you are checking whether it was chosen. An estimator who names a figure and explains what drove it has looked at your valleys. One who says “we always use ten” has looked at a template.
Which product, and what coverage does its data sheet publish per square?
Bundles per square and coverage per square are printed on every data sheet and vary between products in the same manufacturer’s line. If the order was built at 100 square feet per square for a product published at 98.4, it is short by about 1.6 percent — enough to run out on the last slope of a large roof.
What exposure will these be installed at, and does that match the manufacturer’s instructions for my slope?
On wood roofs this changes the material quantity outright. On asphalt it changes whether the warranty and the tested assembly still apply. Either way, it is a number the estimator already knows.
Are starter, hip and ridge, valley material, drip edge, and flashing inside the per-square price, or separate lines?
These are bought by the linear foot, not by the square, so they can be entirely absent from a per-square price without the number looking wrong. This is the most common way two quotes with the same unit price turn out to be different jobs.
How did you measure — aerial report, plan set, or hand measurement — and can I have a copy?
An aerial or plan-based takeoff can be handed over and checked against the other proposals. A number with no method behind it cannot be checked at all, and it is the one most likely to move after the tear-off starts.
Require these in writing
- Measured roof surface, in square feet, stated separately from any waste allowance
- The waste percentage used, as a percentage
- Total squares, labeled as measured surface or as order area
- The product name and the coverage per square its data sheet publishes
- Weather exposure the shingles will be installed at
- Linear feet of eave, rake, hip, and ridge, with the accessory product named for each
- Number of tear-off layers included, and the price per additional layer if more are found
- Deck replacement allowance: the unit, the rate, and how it is measured and documented
Where the number goes wrongSection link
Common misconceptions
Common belief
A square is 100 shingles.
What is actually true
It is 100 square feet of roof surface. The piece count in a square is whatever the product’s geometry requires — 64 for several metric laminates, 65 for others, 80 for a 12 × 36 inch three-tab, 60 for one manufacturer’s laminate designed to make three bundles reach exactly 100 square feet.
Common belief
Three bundles always make a square.
What is actually true
Three is the most common count for asphalt laminates, but Owens Corning’s own guide specification lists Duration Premium at four bundles of 16 and TruDefinition Duration at three bundles of 20 or 22 — same 64 pieces, same 98.4 square feet, different packaging. Cedar shingles come four bundles to a square; 18-inch cedar shakes five — and changing the pack from 12/12 to 9/9 changes what those five bundles cover without changing the count at all.
Common belief
A square of shingles covers 100 square feet.
What is actually true
Frequently not. Owens Corning publishes 98.4 square feet per square for its Duration laminates, and CertainTeed publishes the same figure for Landmark. IKO markets against exactly this, stating that a competitor’s three bundles “may only cover about 98.4 square feet” while it packs 20 shingles per bundle “for an absolute 100 square feet.” Two manufacturers’ technical documents confirm the 98.4 figure independently of that marketing claim.
Common belief
The two quotes list different square counts, so one of them measured wrong.
What is actually true
More often one included waste and the other did not. Compare the measured surface, not the printed square count, before concluding anyone made an error.
Common belief
My house is 2,000 square feet, so my roof is 20 squares.
What is actually true
Living area is not footprint, footprint is not roof surface, and roof surface is not order area. A two-story 2,000 square foot house might have a 1,000 square foot footprint and, at 6:12, about 11.2 squares of roof — a little over half the guess.
How it actually fails
- Waste applied twice
- Someone takes the square count off a proposal that already includes a waste allowance and adds waste again before ordering. On the example roof that turns 22.1 squares into 24.4 and 68 bundles into 75.What you can see: Whole pallets left over at the end of the job; a stated square count noticeably larger than footprint × pitch factor ÷ 100 for a simple roof.
- Ordering at 100 square feet per square for a 98.4 product
- The order is built on the unit rather than on the product’s published coverage. The shortfall is about 1.6%, which is invisible on a small roof and about half a square on a 30-square one. On the example roof it is the difference between 67 bundles and the 68 actually needed.What you can see: The crew runs short on the final slope; the reorder arrives from a different production run and the last courses do not quite match.
- Exposure stretched to make the bundles reach
- Rather than order one more bundle late in the day, the courses are run slightly wider. Headlap drops, the tested assembly no longer matches what was tested, and the manufacturer’s installation instructions — the condition the warranty runs on — are no longer satisfied.What you can see: Course spacing that widens toward the ridge, visible in raking light or from across the street; a bundle count on the delivery ticket that is short of the proposal’s own square count.
- Squares counted from the footprint
- The pitch multiplier is skipped, usually because the number came off an aerial outline or a plan without a slope noted. The order is short by the whole slope correction — 212 square feet on the example roof, or 14 bundles.What you can see: A square count that matches the building’s footprint divided by 100 almost exactly; a proposal with no pitch recorded anywhere on it.
- Accessories missing from a per-square price
- Starter, hip and ridge, valley material, drip edge, and step flashing are bought by the linear foot. A per-square rate can exclude all of them and still look like a complete number.What you can see: A proposal with a square count and a total but no linear-foot quantities anywhere; a change order for edge metal after the tear-off.
Sources and further readingSection link
Understanding Roofing / Published / Updated
Scope and limitations
- It cannot tell you how many squares your roof is.
- That requires a measurement of every plane on this specific building, with its pitches, and no table can substitute for one.
- It publishes no price per square.
- The dollar figures in the normalization example are invented inputs chosen to make the arithmetic visible, and carry no market meaning.
- It publishes no waste percentage, because the right allowance depends on the geometry of the roof in front of you.
- Where a number was needed for the worked example, 10% was assumed openly and labeled as an assumption.
- The coverage and packaging figures are what named manufacturers and the Cedar Shake & Shingle Bureau published for named products on the dates recorded below.
- Packaging changes.
- Check the bundle wrapper and the current data sheet for the product actually being installed.
- It cites no code provision.
- Exposure, headlap, layer limits, underlayment, and ice-barrier requirements come from the code edition your jurisdiction has adopted and amended, plus the manufacturer’s instructions — confirm both with your building department.
Section 073113 — Fiberglass-Based Asphalt Shingles & Accessories (guide specification)
Owens Corning Roofing and Asphalt, LLC
Bundles per square and coverage per square varying between products in one manufacturer’s catalog: TruDefinition Duration at 3 bundles of 20 or 22 and 98.4 sq ft; Duration Premium at 4 bundles of 16 and 98.4 sq ft; Supreme 12 × 36 in at 3 bundles of 26, 27, 27 and 100.0 sq ft; Supreme metric at 3 bundles of 21, 22, 22 and 100.0 sq ft; Berkshire at 5 bundles of 9 and 99.5 sq ft; Woodmoor and Woodcrest at 6 bundles of 15 and 100.0 sq ft. Also underlayment listed by the roof square (4, 5, and 10 squares per roll), mineral surface roll at 1 roll per square, and starter supplied as strips measured in feet.
Product-specific, one manufacturer, and written as a specifier’s template rather than as field instruction. It is not a code determination and it does not describe any other brand’s packaging.
Technical Data Sheet — Landmark Shingles
CertainTeed LLC / August 2024
3 bundles per square, 65 shingles per square, approximate coverage per square of 98.4 square feet, weight of 211 to 225 lb per square, and the ASTM E108 / UL 790, ASTM D3161 and ASTM D7158 listings quoted in the warranty section.
This is a distributor-hosted copy of CertainTeed’s own data sheet; CertainTeed serves the file through a search interface rather than a stable direct URL. Weight is stated as dependent on manufacturing location.
Timberline HDZ Shingles — product specification (RESGN467HDZ)
GAF / ©2019 GAF
3 bundles per square and 64 pieces per square at 13¼ × 39⅜ inches with a 5⅝ inch exposure, and the instruction that Timberline HDZ and Timberline HD may be mixed on one roof only when the six-digit codes on the end of the bundle match.
GAF’s own document server refuses automated retrieval, so the copy cited and read here is the one filed with a municipal historic preservation commission. It is GAF’s document, unaltered, but it is a 2019 revision and packaging may have changed since.
Technical Data Sheet — Cambridge
IKO Industries / December 2024
Cambridge at 20 shingles per bundle, 33.3 sq ft coverage per bundle, 100 sq ft per three bundles, 40⅞ in length by 13¾ in width, and 5⅞ in exposure — the dimensions that let 60 pieces reach a full 100 square feet.
Product-specific and one manufacturer. Coverage is a packaging figure, not a statement about any roof’s measured area.
How Many Bundles of Shingles Are in a Square?
IKO Industries
A manufacturer stating plainly that a competitor’s three bundles “may only cover about 98.4 square feet,” and that IKO packs “exactly 20 IKO laminated shingles in every bundle for an absolute 100 square feet.”
Marketing content written by a manufacturer about its competitors. It is used only for IKO’s statement about its own packaging and as evidence that the discrepancy is well known in the industry; the 98.4 figure it attributes to competitors is confirmed independently by Owens Corning’s and CertainTeed’s own technical documents.
Coverage and Exposure Tables — New Roof Construction Manual (2025)
Cedar Shake & Shingle Bureau / May 2025
Coverage of one four-bundle square of cedar shingles at different exposures (70, 80, 90 and 100 sq ft for 16-inch shingles); maximum exposures by slope and grade; the note that a 9/9 shake pack gives 75% of the coverage of a 12/12 pack; and the bureau’s worked reduced-exposure formula, “a 4-bundle square at 4″ exposure covers 80 square feet. 3200 divided by 80 = 40 squares of material.”
Applies to Certi-label western red cedar products only. The bureau prints its own caveat on the same page: check with the building code official for local jurisdiction requirements.
Fall Protection — Overview
U.S. Occupational Safety and Health Administration
That falls are among the most common causes of serious work-related injuries and deaths, and that OSHA requires fall protection at elevations of six feet in the construction industry.
OSHA standards govern employers and workers, not homeowners on their own property. They are cited here as evidence of the hazard, not as a rule that applies to a resident.