Roofing is the job where the container has to be on site before the first shingle comes off, because the debris arrives all at once and there is nowhere to put it. It is also the job where the weight is easiest to get wrong.
Two things drive the number. Pitch, because a sloped roof has more surface than the footprint it covers. And layers, because a roof that has been shingled over more than once weighs roughly what you would expect that many roofs to weigh.
Squares, pitch and layers
Roofers measure in squares. One square is 100 square feet of roof surface. A straightforward 1,500 square foot ranch with a 6/12 pitch works out to about 16.8 squares, not 15, because the slope adds roughly 12 percent.
You can measure the footprint from the ground. The calculator applies the pitch multiplier for you, so you do not need to get on the roof with a tape.
Roof pitch multipliers
The multiplier is geometry, not a rule of thumb: for a roof rising r inches over 12, it is the square root of 1 plus (r/12) squared. Multiply your ground footprint by it to get the actual roof surface. These are the exact figures the calculator above uses, worked here against a 1,500 square foot footprint.
| Pitch | Multiplier | 1,500 sq ft becomes | Squares |
|---|---|---|---|
| Flat / low slope | 1.000 | 1,500 sq ft | 15.0 |
| 2/12 | 1.014 | 1,521 sq ft | 15.2 |
| 3/12 | 1.031 | 1,546 sq ft | 15.5 |
| 4/12 (gentle) | 1.054 | 1,581 sq ft | 15.8 |
| 5/12 | 1.083 | 1,625 sq ft | 16.3 |
| 6/12 (common) | 1.118 | 1,677 sq ft | 16.8 |
| 7/12 | 1.158 | 1,737 sq ft | 17.4 |
| 8/12 (steep) | 1.202 | 1,803 sq ft | 18.0 |
| 9/12 | 1.250 | 1,875 sq ft | 18.8 |
| 10/12 (steeper) | 1.302 | 1,953 sq ft | 19.5 |
| 11/12 | 1.357 | 2,036 sq ft | 20.4 |
| 12/12 (very steep) | 1.414 | 2,121 sq ft | 21.2 |
Pitch matters more than people expect at the steep end. A 12/12 roof has 41 percent more surface than the footprint it sits on, so the same house plan can be six squares heavier than the flat-roofed version of itself.
What a square weighs
These are tear-off weights: what actually lands in the container, which is not what the same material weighed when it went on. The calculator above uses these exact figures.
| Shingle | Tear-off lbs per square | Notes |
|---|---|---|
| 3-tab asphalt | 230 | The lightest common option, and the one ARMA’s benchmark is built on. |
| Architectural asphalt | 300 | What sits on most modern roofs around here. |
| Premium / designer laminate | 400 | Heavy laminates, sold four bundles to the square instead of three. |
| Wood shake | 400 | Bulky rather than dense. Usually fills the container before it reaches the tonnage. |
| Slate | 1,170 | Masonry, so it cannot go in a standard container. Thickness drives this hard. |
| Clay or concrete tile | 950 | Masonry. Needs a dedicated haul to a processing facility. |
The Asphalt Roofing Manufacturers Association puts a typical single-layer asphalt replacement at 2.5 pounds per square foot, which is 250 pounds per square. That is the benchmark worth checking any roofing calculator against, including this one.
Why tear-off weighs more than new shingles
There is a widespread idea that tear-off weighs double the new material. It does not. The realistic gap is 15 to 25 percent, roughly 30 to 60 pounds a square, and it comes from three things you can point at.
- The underlayment comes off with it. Number 15 felt does not weigh 15 pounds a square despite the name. It is nearer 7 to 13.
- Ice and water shield is the heavy one. At about 27 pounds per 100 square feet it is over three times the weight of felt, and on a Massachusetts roof it often covers a fifth of the deck or more. This is the line most calculators written for warmer states simply do not have.
- Nails and absorbed moisture. Fasteners add a couple of pounds a square. Water is why a roof stripped the morning after rain weighs noticeably more than the same roof in a dry week.
Drip edge and flashing barely register. The thing that genuinely moves the number is rotten sheathing: if plywood is coming off with the shingles, add its weight separately using the weight calculator at 350 pounds per cubic yard for wood. That is the one item capable of turning a comfortable container into a tight one.
Worth knowing where our numbers come from: most shingle manufacturers publish pieces and bundles per square but not weight. CertainTeed is the exception, and its own data sheets carry the note "dependent on manufacturing location", so the same shingle genuinely weighs differently from different plants. Treat any single printed figure, ours included, as nominal.
How many bundles in a square
Three bundles to the square is the familiar answer, and it is right for standard 3-tab and standard architectural. It is wrong for everything heavier.
| Shingle | Bundles per square | A square, new | Per bundle |
|---|---|---|---|
| 3-tab asphalt | 3 | about 200 lbs | about 67 lbs |
| Architectural asphalt | 3 | about 220 lbs | about 73 lbs |
| Premium / designer laminate | 4 | about 300 lbs | about 75 lbs |
| Wood shake | 5 | about 300 lbs | about 60 lbs |
| Slate | Not sold in bundles | — | — |
| Clay or concrete tile | Not sold in bundles | — | — |
The reason is that a bundle weighs about 70 pounds whatever the shingle. A bundle is sized to what one person can carry up a ladder, so a heavier product is split into more bundles rather than heavier ones. Premium laminates go four to the square and designer lines can run five or six, so a calculator that assumes three will under-order the exact roofs where it matters most.
One more thing worth knowing before you order: a "square" of most laminated shingles covers 98.4 square feet rather than a true 100. On a 30 square roof that is about half a bundle short. The bundle count in the calculator already carries 10 percent for waste and cuts, which absorbs it.
The layer question
Massachusetts has plenty of houses carrying two layers and a fair number carrying three. You can usually tell from the rake edge or by lifting a shingle at the eave. If you are not sure, count on two and be pleasantly surprised.
Tell us the layer count when you book. It is the single most useful thing you can say about a roofing job, and it is the difference between one container and two.
Questions about this tool
How many squares is my roof?
Measure the footprint in square feet, apply the pitch multiplier, then divide by 100. The calculator does all three steps once you enter the footprint and pick a pitch.
How many bundles of shingles do I need?
Three bundles per square for standard 3-tab and standard architectural, four for premium laminates and five for wood shake. Multiply your squares by that, then add about 10 percent for waste and cuts. The calculator prints the figure for you. It covers field shingles only, so starter strip and ridge cap are ordered on top.
How much does a bundle of shingles weigh?
About 70 pounds, and that holds for almost any asphalt shingle. A bundle is sized to what one person can carry up a ladder, so a heavier product gets split into more bundles rather than heavier ones. Standard 3-tab runs nearer 67 pounds a bundle and a premium laminate nearer 75.
How much does a square of shingles weigh?
New, about 200 pounds for 3-tab and 220 for standard architectural, rising to 300 for premium laminates. Coming off a roof it is heavier: roughly 230 and 300 respectively, because the tear-off carries the felt, the nails and whatever moisture the old shingles have absorbed.
What size dumpster for a roof tear-off?
It depends far more on layers and shingle type than on the size of the house. A single layer of 3-tab on a small ranch is very different from three layers of architectural. Run the numbers above and take the larger size if it lands close.
Can I put slate or tile roofing in the container?
No. Slate and clay or concrete tile are masonry, which is banned from disposal in Massachusetts and needs a processing facility. Asphalt and wood shingles are fine.
Should the container be on site before we start?
Yes. Tear-off debris arrives faster than anything else we haul and there is rarely anywhere to stage it. Book the delivery for the morning the crew starts.