Materials · no ZIP code asked
Roofing calculator
Measure the roof from above, choose the pitch and the shingle: squares, bundles, underlayment rolls, starter and ridge show up at once.
Built by Radif Partners · How prices are built · Editorial policy
Shingle bundles
74
24.6 squares to cover (2,236 sq ft of roof surface, pitch factor 1.118)
| Roof surface | 2,236 sq ft |
| With your allowance | 2,460 sq ft |
| Synthetic underlayment rolls | 3 |
| Starter strip bundles | 2 |
| Hip and ridge cartons | 3 |
Bundles per square, starter (105 ft a bundle), ridge (20 ft a carton) and underlayment (10 squares a roll) follow one manufacturer’s published figures; check the wrapper of the product you buy. How this is calculated.
A roof that covers 2,000 square feet seen from above, overhangs included, has 2,236 square feet of surface at a 6/12 pitch, because the slope stretches every foot of run by a factor of 1.118. With a 10% allowance for cuts, hips and valleys, that is 24.6 squares of 100 square feet and 74 bundles of architectural shingles at 3 bundles per square, the figure Owens Corning publishes for its laminated lines; a premium heavyweight shingle packed 4 bundles per square takes 99. The same calculator counts 3 rolls of synthetic underlayment at 10 squares a roll, 2 bundles of starter strip for 180 feet of eaves and rakes at 105 feet per bundle, and 3 cartons of hip and ridge caps for 50 feet at 20 feet per carton. A shallower 4/12 roof on the same house needs 70 bundles, a 10/12 roof 86. Type the price per bundle from your supplier to total the shingles.
Footprint times pitch factor
You do not need to climb up to measure a roof. Measure the outline of the roof from the ground, including the overhang of the eaves and rakes, and multiply length by width; on a simple rectangle that is the footprint. Then pick the pitch, the rise in inches for every 12 inches of horizontal run, which you can read with a level and a tape at the gable end or from the attic. The calculator multiplies the footprint by the pitch factor, the square root of 1 plus (rise/12) squared, which is the length of a rafter for each foot of run.
That shortcut has a useful property: for a roof where every plane has the same pitch, the factor applies to the whole footprint whatever the shape. A hip roof and a gable roof over the same 2,000 square feet at 6/12 both carry 2,236 square feet of shingles. What changes is the waste: hips and valleys mean more cut shingles, so raise the allowance for a cut-up roof. Dormers or a porch at a different pitch should be measured separately and added.
| Pitch | Factor | Roof surface | Squares (+10%) | Bundles, 3 per sq | Bundles, 4 per sq |
|---|---|---|---|---|---|
| 2/12 | 1.014 | 2,028 sq ft | 22.3 | 67 | 90 |
| 3/12 | 1.031 | 2,062 sq ft | 22.7 | 69 | 91 |
| 4/12 | 1.054 | 2,108 sq ft | 23.2 | 70 | 93 |
| 5/12 | 1.083 | 2,167 sq ft | 23.8 | 72 | 96 |
| 6/12 | 1.118 | 2,236 sq ft | 24.6 | 74 | 99 |
| 7/12 | 1.158 | 2,315 sq ft | 25.5 | 77 | 102 |
| 8/12 | 1.202 | 2,404 sq ft | 26.4 | 80 | 106 |
| 9/12 | 1.250 | 2,500 sq ft | 27.5 | 83 | 110 |
| 10/12 | 1.302 | 2,603 sq ft | 28.6 | 86 | 115 |
| 12/12 | 1.414 | 2,828 sq ft | 31.1 | 94 | 125 |
What a square and a bundle hold
Roofers price and order in squares, 100 square feet of roof. The Owens Corning guide specification, revised in January 2026, gives the packaging line by line. Its Supreme three-tab shingle comes 3 bundles to a square, 80 shingles at a 5 inch exposure covering 100 square feet. TruDefinition Duration, a laminated architectural shingle, also comes 3 bundles to a square, but 64 shingles cover 98.4 square feet, a detail that matters on a very large roof. Duration Premium, a heavier shingle, is packed 4 bundles of 16 to the square, which is why the shingle type changes the bundle count without changing the area. Other brands package differently; read the coverage on the wrapper and adjust the type if needed.
Underlayment, starter and ridge
The same specification lists RhinoRoof U20 synthetic underlayment at 10 squares a roll, the figure the calculator uses, and ProArmor at 9.29 squares, so switching products can change the roll count on a large house. Starter Strip Plus gives about 105 linear feet a bundle for the first course along the eaves and rakes, and DuraRidge hip and ridge caps cover 20 linear feet a carton. Measure the eaves and rakes as the perimeter of the roof edge and the hips and ridges along their slope. A small ranch of 1,200 square feet at 5/12 in three-tab shingles comes to 14.3 squares and 43 bundles, before starter and ridge.
Materials list versus the roofer's quote
The bundle count is what a supplier needs to deliver, and it helps you check a written estimate line by line. It is not the price of the job. A professional roof replacement had a median of $11,450 in August 2026 dollars in the 2023 American Housing Survey, with half of jobs between $7,050 and $17,590; the roof replacement cost page adjusts that by state and house size. Labor is the other large part: BLS counted 135,490 roofers in May 2025, paid $27.95 an hour on average. Tear-off of old layers, rotten decking, drip edge, flashing, vents and disposal are priced on top of the shingles. Ask the contractor for the number of squares on the estimate; if it is far from the figure here at the same pitch, ask how it was measured.