Roof Shingle Calculator [Squares, Bundles & Pitch]

Eaves	84 lf
Rakes	72 lf
Ridge	42 lf

To calculate roof shingles, multiply the roof footprint (with overhangs) by the slope factor for your pitch, add a waste allowance, divide by 100 to get squares, and multiply by 3 bundles per square. A 40 × 30 ft gable house with 1 ft overhangs at a 6/12 pitch has 1,503 ft² of roof: 16.5 squares with 10% waste, or 50 bundles.

Use it if you are buying shingles for a reroof, checking a roofer's material list, or pricing a shed or garage. Enter the house length, width, overhang and pitch for a gable, hip or shed roof. For an L-shaped or cut-up roof, enter each plane measured on the surface. You get squares, bundles, shingle pieces, starter strip, ridge cap, underlayment rolls, drip edge pieces and nails. Each count uses manufacturer figures for GAF Timberline HDZ or Owens Corning Duration, or your own coverage.

How to use the shingle calculator

Pick the roof shape. Gable, hip and shed use the footprint; “Measured planes” takes each slope's length and width measured on the roof.
Enter the house length and width and the level overhang on each side. Eaves and rakes often differ; use the average.
Enter the pitch as rise in 12. The roof pitch calculator converts degrees or a rise-and-run measurement.
Leave waste blank to use the default for the shape, or type your own.
Pick the shingle line, or choose “Other” and type the coverage printed on the bundle. Override the starter and ridge-cap coverages if your accessories differ.

The formula: squares and bundles

Roof area = (length + 2 × overhang) × (width + 2 × overhang) × slope factor, where the slope factor is √(rise² + 12²) ÷ 12. Hip and gable roofs at the same pitch have the same area for the same footprint, because every plane is tilted by the same angle. Squares = roof area × (1 + waste %) ÷ 100. Bundles = squares × 100 ÷ coverage per bundle, rounded up.

The coverage comes from the data sheets. GAF gives Timberline HDZ as 64 pieces and 3 bundles per square with a 5 5/8 in exposure on a 13 1/4 × 39 3/8 in shingle. Owens Corning gives TruDefinition Duration the same size and exposure, 3 bundles per square, and states the coverage as 98.4 ft² per square. That figure checks out: 64 × 39.375 in × 5.625 in = 98.44 ft². So “3 bundles per square” is the nominal rule, and the calculator uses 33.33 ft² per bundle for GAF and 32.8 ft² for Owens Corning.

Roof pitch multiplier table

Multiply the footprint by the factor to get the roof surface. The same factors drive our roof pitch chart, which runs from 1/12 to 24/12.

Pitch	Angle	Multiplier	1,000 ft² footprint =	Bundles (no waste)
2/12	9.5°	1.014	1,014 ft²	31
3/12	14°	1.031	1,031 ft²	31
4/12	18.4°	1.054	1,054 ft²	32
5/12	22.6°	1.083	1,083 ft²	33
6/12	26.6°	1.118	1,118 ft²	34
7/12	30.3°	1.158	1,158 ft²	35
8/12	33.7°	1.202	1,202 ft²	37
9/12	36.9°	1.25	1,250 ft²	38
10/12	39.8°	1.302	1,302 ft²	40
12/12	45°	1.414	1,414 ft²	43

Squares and bundles by roof size

A square of shingles is 100 ft² of roof. With 3 bundles per square (GAF Timberline HDZ coverage):

Roof area	Squares	Bundles, no waste	+10% waste	+15% waste
500 ft²	5	15	17	18
1,000 ft²	10	30	33	35
1,200 ft²	12	36	40	42
1,500 ft²	15	45	50	52
1,800 ft²	18	54	60	63
2,000 ft²	20	60	66	69
2,400 ft²	24	72	80	83
2,500 ft²	25	75	83	87
3,000 ft²	30	90	99	104
3,500 ft²	35	105	116	121
4,000 ft²	40	120	132	138

Calculating roof shingles: three worked examples

Gable: 40 × 30 ft, 1 ft overhang, 6/12

Footprint 42 × 32 = 1,344 ft² × 1.118 = 1,503 ft². With 10% waste: 16.53 squares = 50 bundles. Eaves 84 lf and rakes 71.6 lf take 2 bundles of Pro-Start and 16 ten-foot pieces of drip edge. The 42 ft ridge needs 2 bundles of ridge cap at 25 lf each. Underlayment: 2 rolls. Nails: about 4,232.

Hip: 50 × 30 ft, 1 ft overhang, 5/12

Footprint 52 × 32 = 1,664 ft² × 1.0833 = 1,803 ft². With 15% waste: 20.73 squares = 63 bundles. A hip roof has no rakes, but its four hips add 94.4 lf to the 20 ft ridge, so ridge cap is 114 lf = 5 bundles. Starter runs the whole 168 ft perimeter: 2 bundles.

Low-slope ranch: 60 × 28 ft, 1 ft overhang, 3/12

1,917 ft² of roof, 21.09 squares, 64 bundles. Because 3/12 is between 2:12 and 4:12, the IRC requires double underlayment, so the count rises to 5 rolls instead of 3.

Measured planes

Two gable planes of 42 × 17.9 ft plus a triangular hip end 20 ft wide and 12 ft tall (entered as 20,12,t) total 1,624 ft², or 55 bundles with 12% waste. Measure each plane along the slope from eave edge to ridge.

Starter strip, ridge cap, underlayment, drip edge and nails

Starter strip goes along the eaves and rakes; GAF describes Pro-Start as helping resist blow-off “at eaves and rakes.” Pro-Start covers about 120.33 lf per bundle and Owens Corning Starter Strip Plus about 105 lf.
Ridge cap covers ridges and hips. Coverage depends on the exposure: Owens Corning DuraRidge is 20 lf per carton at an 8 in exposure, and GAF Seal-A-Ridge is sold as 25 lf per bundle. Hip length on a regular hip roof is half the width × √(2 + (rise ÷ 12)²) per hip.
Underlayment: at 4/12 and steeper the IRC calls for one layer lapped 2 in. Owens Corning's 250 ft × 48 in Deck Defense roll covers 937 ft² with a 3-in lap. From 2/12 up to 4/12 two layers are required, each course lapped half the width plus 2 in, so a roll covers about 250 × 22 in = 458 ft². Ice-barrier membrane at the eaves, where the code requires it, is extra.
Drip edge: IRC R905.2.8.5 requires it at eaves and rake edges, with adjacent pieces lapped at least 2 in. Each 10 ft piece therefore covers 9.83 ft.
Nails: IRC R905.2.5 calls for galvanized, stainless, aluminum or copper roofing nails with at least a 12-gage shank and 3/8 in head, long enough to go 3/4 in into the sheathing (or through it). R905.2.6 requires at least four per strip shingle; follow the wrapper if it asks for more.

Common mistakes

Using the house's square footage. Living area counts every floor. Use the footprint of the roof, including overhangs and porches.
Forgetting the pitch. A 10/12 roof has 30% more surface than its footprint.
Counting starter and ridge as field shingles. They are separate products with their own coverage. Cutting 3-tab shingles for starter is a different method.
Assuming 3 bundles everywhere. Heavier designer lines can be 4 or 5 bundles per square. Read the wrapper.
Skipping double underlayment on low slopes. Between 2/12 and 4/12 the code requires it, and below 2/12 shingles are not allowed at all.

Price the job with the roof replacement cost calculator. For walls, the siding calculator uses the same squares, and the renovation cost calculator totals other projects.

Frequently asked questions

How many bundles of shingles are in a square?

Three for most architectural shingles. GAF lists Timberline HDZ at 3 bundles and 64 pieces per square, and Owens Corning lists TruDefinition Duration at 3 bundles per square covering 98.4 ft². One bundle covers about 33.3 ft² (GAF) or 32.8 ft² (Owens Corning). Some heavier designer shingles pack 4 or more bundles per square, so read the wrapper.

What is a square of shingles?

A roofing square is 100 square feet of roof surface. Roofers price and order by the square: a 2,000 ft² roof is 20 squares, or 60 bundles at 3 bundles per square before waste.

How do I calculate shingles for my roof?

Measure the footprint including overhangs, multiply by the slope factor for the pitch (√(rise² + 144) ÷ 12), add a waste allowance, divide by 100 for squares and multiply by bundles per square. A 40 × 30 ft gable with 1 ft overhangs at 6/12 has 1,503 ft² of roof; with 10% waste that is 16.53 squares, or 50 bundles.

How many bundles of shingles do I need for 1,000 square feet?

30 bundles at 3 bundles per square (33.33 ft² each) with no waste, or 33 with 10% waste. Those 1,000 ft² must be roof surface, not floor area: a 1,000 ft² footprint at 6/12 is 1,118 ft² of roof.

How many squares is a 2,000 sq ft house?

It depends on the footprint and the pitch, not the living area. A single-story 2,000 ft² footprint at 6/12 with no overhang is 22.4 squares of roof (24.6 with 10% waste); at 8/12 it is 24 squares. A two-story 2,000 ft² house has roughly half that footprint.

How much starter strip and ridge cap do I need?

Starter runs along eaves and rakes; GAF says Pro-Start provides about 120.33 linear feet per bundle and Owens Corning gives about 105 for Starter Strip Plus. Ridge cap covers every ridge and hip: Owens Corning DuraRidge covers 20 lineal feet per carton, and GAF Seal-A-Ridge is sold as 25 lineal feet per bundle. On the 40 × 30 ft example that is 156 lf of starter (2 GAF bundles) and 42 lf of ridge (2 bundles).

How many rolls of underlayment do I need?

Divide the roof area by the roll's coverage. Owens Corning lists a 10-square Deck Defense roll at 937 ft² with a 3-in lap. Between 2/12 and 4/12 the IRC requires two layers lapped half a sheet plus 2 in, so a 48-in roll covers only about 458 ft²: roughly twice the rolls.

How many nails per square of shingles?

GAF lists 256 nails per square for Timberline HDZ, which is 4 per shingle × 64 shingles. The IRC (R905.2.6) sets a minimum of 4 fasteners per strip shingle, or more if the manufacturer's instructions require it. The 16.5-square example needs about 4,232 nails.

How much waste should I add for shingles?

There is no code or manufacturer figure for waste. This calculator defaults to 10% for gable and shed roofs, 15% for hip roofs and 12% for measured planes as planning assumptions, because hips and valleys need more cut pieces. Replace it with your roofer's number.

What is the lowest pitch I can use shingles on?

2/12 (about 9.5°). The IRC (R905.2.2) allows asphalt shingles from 2:12, with double underlayment required from 2:12 up to 4:12. The calculator switches the underlayment count automatically.

Sources & method

Results are estimates for general information. Found an error? It helps everyone — see our methodology.

Roofing Shingles Calculator: Squares & Bundles