Measurement
A roofing square is one hundred square feet, and your roof is bigger than your house
Roofing is sold by the square because it is a convenient bundle size and because it has been that way for a very long time. Understanding the unit is the difference between reading an estimate and being read to.
The unit itself
One square is 100 square feet of finished roof surface: a ten-foot by ten-foot patch. Shingles are packaged so that three bundles typically cover a square on standard architectural products, though heavier profiles take four or five. Underlayment, ice and water shield, ridge cap and starter are all quantified against the same measure, which is why a scope that names squares is a scope you can check.
A typical single-family roof in this market runs somewhere between twenty and forty squares once the pitch and the waste are accounted for. That is a range, not an estimate of yours, and the point of the rest of this page is why the number for your house is what it is.
Why the roof is bigger than the house
A roof plane is a slope, and a slope covering a given footprint is longer than the footprint. The steeper it is, the longer it gets. The conversion is a pitch multiplier applied to the plan area:
| Pitch | Multiplier applied to plan area | A 2,000 square foot footprint becomes |
|---|---|---|
| 4:12 | about 1.054 | about 21 squares before waste |
| 6:12 | about 1.118 | about 22 squares before waste |
| 8:12 | about 1.202 | about 24 squares before waste |
| 10:12 | about 1.302 | about 26 squares before waste |
| 12:12 | about 1.414 | about 28 squares before waste |
Add the overhangs, which are roof but are not house, and the difference grows further. Roof pitch explains what those numbers mean and what else changes as they climb.
How a roof gets measured
- On the roof, with a tape
- Plane by plane, the traditional method and still the most reliable on a complicated roof. It also puts somebody on the roof, which is where the rest of the inspection happens anyway.
- From the ground, with a pitch reading
- Measure the footprint and the overhangs, establish the pitch with a level and a rule or from inside the attic, and apply the multiplier. Accurate enough on a simple gable.
- Aerial or satellite measurement
- A report generated from imagery, giving plane areas, ridge and valley lengths and pitch. Good on straightforward roofs, and it can be wrong about pitch changes, small dormers, and anything under tree cover.
- Drone imagery
- Useful for photographs of condition, and for measurement where the roof is unsafe to walk. Still needs somebody who knows what they are looking at.
Any of these is fine. What is not fine is a scope with no square count in it at all. Squares is the quantity every other line depends on, and a quote without it cannot be compared with anything.
Waste, and why it is not padding
Material has to be cut. Every hip, valley, rake and penetration produces offcuts that cannot be used elsewhere, and a starter course consumes material along the whole eave and rake. Waste is expressed as a percentage on top of the measured squares.
- A simple gable roof wastes little. Long straight courses and two rakes.
- A hip roof wastes noticeably more, because every course is cut at both ends against a hip line.
- A cut-up roof with valleys and dormers wastes the most, and the figure climbs with the number of intersections rather than with the area.
- Steep roofs waste slightly more, because material handling is harder and offcuts are less recoverable.
A waste figure in the region of ten percent on a simple roof and considerably more on a complex one is ordinary. A scope with no waste allowance is a scope that will run short, and a job that runs short in the afternoon either gets a partial second delivery or gets finished with something not quite the same.
What squares tell you when you are comparing quotes
- Two quotes with different square counts are measuring different roofs. One of them is wrong, and it is worth finding out which before comparing anything else.
- A square count with no pitch stated is incomplete. Pitch changes the area, the labor and the access.
- Ridge, hip and valley lengths matter separately. Ridge cap and valley treatment are priced by the foot, not by the square, and a hip roof has a lot of both.
- Penetration counts belong in the scope. Each pipe boot, each vent, each skylight is its own detail and its own potential leak.
- Tear-off is quantified in squares too, and in layers. Two layers coming off is twice the tear-off, twice the disposal, and it is not covered by a single "tear off existing" line.
That comparison is the whole subject of how to read a roofing estimate, and the factors behind the differences are in what drives roof cost.
Want your roof measured and the count written down where you can see it?
Request a free inspectionCan I work out my own square count?
On a simple gable, roughly, yes: measure the footprint including overhangs, establish the pitch, apply the multiplier from the table above and divide by 100. On a hip roof with dormers and valleys, an estimate done from the ground will be out by enough to matter, and the useful version comes from somebody measuring the planes.
Why does my neighbor’s roof need fewer squares than mine when the houses look the same?
Pitch, overhang depth and roof geometry. Two houses with identical floor area can differ by several squares if one has a steeper roof or deeper eaves, and a hip roof and a gable roof over the same footprint are not the same area of material.
Is a bigger waste percentage a red flag?
Not by itself. Complexity drives it, and a roofer who has measured a cut-up roof and allowed for it properly is doing the job correctly. What is worth asking is what the figure is based on — valleys, hips and dormers — rather than treating the percentage as a negotiation.
Do squares include the garage and the porch?
They include every plane being roofed, so it depends on what the scope covers. This is worth being explicit about: a detached garage or a porch roof left out of the count and then added later is one of the more common sources of a surprise on a job.
All work is performed by licensed and insured local roofing professionals.