Roofing Shingle Calculator
Squares and bundles of shingles from footprint and pitch.
Measure at the eaves, including overhangs.
10% for simple gable roofs, 15% for roofs with hips, valleys, or dormers.
You need
45 bundles
Assumes 3 bundles per square, standard for architectural shingles.
- Roof area (with waste)
- 1,476 sq ft
- Roofing squares
- 14.8 squares
- Synthetic underlayment
- 2 rolls
Estimates only. Verify quantities before ordering.
How this is calculated
Roof area = footprint x pitch multiplier x (1 + waste), where the multiplier is sqrt(1 + (rise/12)^2). Squares = area / 100. Bundles = squares x 3, rounded up, since standard architectural shingles pack three bundles per square. Underlayment assumes a 10-square synthetic roll.
Roofers measure in squares, where one square is 100 square feet of roof surface. This calculator starts from your home's footprint (the area the building covers on the ground, including eave overhangs), scales it up by a pitch multiplier to account for the slope, adds waste, and converts the result into squares, shingle bundles, and underlayment rolls.
Pitch is written as rise over run: a 6/12 roof rises 6 inches for every 12 inches of horizontal distance. You can measure it from inside the attic with a level and a tape measure. The steeper the pitch, the more actual roof surface sits above the same footprint, which is exactly what the multiplier captures.
Shingles for common roof sizes
Rows assume a 6/12 pitch and 10% waste, with the footprint measured at the eaves. Steeper roofs need more; use the calculator above to adjust pitch.
| Footprint | Bundles | Squares |
|---|---|---|
| 24 x 30 ft (720 sq ft) | 27 bundles | 8.9 squares |
| 26 x 40 ft (1,040 sq ft) | 39 bundles | 12.8 squares |
| 30 x 40 ft (1,200 sq ft) | 45 bundles | 14.8 squares |
| 28 x 48 ft (1,344 sq ft) | 50 bundles | 16.5 squares |
| 40 x 50 ft (2,000 sq ft) | 74 bundles | 24.6 squares |
Shingle types and expected life
Three-tab shingles are flat, uniform, and the cheapest asphalt option, typically warranted 20 to 25 years and lighter in wind resistance. Architectural, also called dimensional or laminate, shingles bond two layers together for a thicker profile and a shadow line, and they typically carry 30 year to lifetime warranties with better wind ratings. The price difference is modest relative to the labor, which is why architectural now dominates residential reroofing.
Premium and designer shingles imitate slate or shake at higher cost and weight. Metal roofing costs considerably more up front, lasts 40 to 70 years, and sheds snow well. Natural slate and clay tile last longest of all and are heavy enough that the roof structure has to be designed or verified for them, which rules them out for many retrofits.
Warranty length describes the product under ideal conditions, not your roof. Ventilation, installation quality, and climate drive actual service life more than the number on the wrapper, and most warranties are prorated in a way that returns little in practice.
Underlayment, ice barrier, and flashing
Underlayment is the secondary water barrier beneath the shingles. Traditional felt is cheap and tears easily when walked on; synthetic underlayments cost more, lay flatter, resist tearing, and are far safer underfoot on a slope. Either way it is not the primary waterproofing, which is the shingles themselves.
In cold climates, self-adhering ice and water barrier along the eaves is required by code in most jurisdictions, typically extending from the edge to at least 24 inches inside the exterior wall line. It seals around fasteners and is what protects the deck when an ice dam forms and forces water back up under the shingles. It also belongs in valleys and around penetrations regardless of climate.
Flashing is where roofs actually leak. Step flashing along walls, counter flashing where the roof meets masonry, valley flashing, and proper boots at pipes and vents do the work at every transition. Reusing old flashing to save money on a reroof is a false economy, since the flashing is usually older than the shingles that just failed.
Ventilation, tear-off, and layovers
A roof needs balanced intake and exhaust ventilation, usually soffit vents low and ridge vents high, in roughly equal area. Without intake, a ridge vent pulls air from the house instead of the soffits and accomplishes little. Poor ventilation cooks shingles from underneath in summer, shortening their life materially, and in winter it lets warm air melt snow that refreezes at the cold eave, which is what forms ice dams.
Most codes permit two layers of asphalt shingles, so a single layover is often legal. It is still usually the wrong choice: it hides deck damage you cannot then inspect or repair, adds weight, traps heat which shortens the life of the new layer, and produces a less even surface. A tear-off costs more in labor and disposal and is what a full-life roof needs.
Order about 10 percent over the calculated squares, more on a complex roof. Hip and ridge caps are a separate purchase counted by the linear foot, valleys and hips generate waste at every cut, and starter strip along the eaves and rakes is its own product rather than shingles cut down, though some roofers still cut their own.
Common questions
What is a square in roofing?
One square equals 100 square feet of roof surface. Shingles, underlayment, and roofing labor are all priced per square, so a 24 square roof means 2,400 square feet of surface to cover, regardless of the shape of the roof.
How many bundles of shingles are in a square?
Standard architectural (dimensional) shingles are packaged three bundles per square. Some heavyweight designer shingles run four or even five bundles per square, so check the wrapper before converting. Three-tab shingles are also three bundles per square.
How do I measure my roof pitch?
In the attic, hold a level horizontally against a rafter, measure 12 inches along the level from where it touches, then measure straight down from the level to the rafter. That vertical distance in inches is your pitch: 6 inches means a 6/12 roof. From outside, a pitch gauge app against the gable edge also works.
How much waste should I add for a roof?
Use 10% for a simple gable roof with two rectangular planes. Roofs with hips, valleys, dormers, or multiple sections cut a lot more shingles, so use 15%. Complex roofs can justify 20%, and valleys also consume extra underlayment and flashing beyond the shingles themselves.