How many bundles of shingles do I need?

Enter the plan footprint of the roof, its pitch, the waste you want to allow and how many bundles the shingles you are buying cover per square. You get the sloped roof area, the squares, the exact bundle count and the number to actually order — with the slope multiplier shown, so the whole chain can be checked by hand.

Size the order

Plan length ft The long side of the footprint, measured flat. Plan width ft The other side of the footprint. Include the overhang if it is to be covered. Roof pitch in 12 Inches of rise per 12 inches of run. A 6/12 is 26.6° and multiplies area by 1.118. Waste allowance % 10% for a plain roof, 15% with hips, valleys or dormers, 20% on a cut-up roof. Bundles per square per 100 sq ft 3 for 3-tab and most architectural shingles; some designer lines run 4 or 5.

Sloped roof area —sq ft

Bundles to order —bundles

Roofing squares —squares

Bundles calculated —bundles

Extra over bare roof —%

Plan area —sq ft

Slope multiplier —×

Spare coverage bought —sq ft

Measure the plan, not the slope. Length and width are the footprint the roof covers, measured flat — include the overhang if you want the overhanging strip covered, because that strip is roof too. Pitch is inches of rise per 12 inches of run. 10% waste is normal for a plain gable, 15% once there are hips, valleys, dormers or a chimney. Bundles per square is printed on the wrapper: 3 for 3-tab and most architectural shingles.

Why the answer is rarely "area divided by 33.3"

Almost every answer to this question online is one sentence long: a square is 100 square feet, a bundle covers about a third of a square, so divide your area by 33.3. The arithmetic is right and the input is wrong. That rule works only on a flat surface, and a roof is not flat. Everything a shingle actually covers sits on a plane tilted up from the footprint, so the first thing that has to happen is the footprint being stretched by the slope — and that stretch is between 3% and 41% depending on pitch, before any waste is added.

There is a second, quieter error in the same sentence: the area people plug in is usually the floor area of the house. A 24 × 40 ft building is 960 sq ft of floor. The same building with a 6/12 roof and a 1 ft overhang has 1,221 sq ft of shingles to buy. The gap between those two numbers is the biggest single source of short orders, and it has nothing to do with the bundle count itself.

The formula, in the order the numbers appear

Bundles come out of five multiplications and one rounding step. Written out, with the plan area in square feet:

bundles = ceil( plan area ÷ 100 × √(1 + (pitch ÷ 12)²) × (1 + waste ÷ 100) × bundles per square )

Plan area — length × width measured flat, including whatever overhang you want covered. This is a footprint, not a surface.
Slope multiplier — √(1 + (pitch ÷ 12)²), the same number tabulated on the hip roof calculator. It comes straight from Pythagoras: 12 in of run with r inches of rise has a rafter length of √(12² + r²), so the sloped area is the flat area times that ratio divided by 12. A 3/12 gives 1.031, a 6/12 gives 1.118, a 12/12 gives 1.414.
Sloped area — plan area × multiplier. This is the real surface the shingles land on, and it is the number that should have been divided by 33.3 all along.
Squares — sloped area ÷ 100. A square is 100 sq ft of finished roof; it is a unit of area, not a count of bundles.
Waste — multiply by 1 + waste ÷ 100. Cut-offs at hips, valleys, rakes and penetrations are material you buy and do not install.
Bundles — squares × bundles per square, then round up. Bundles per square is a packaging figure, not geometry.

Every step above is a separate output in the calculator, including the multiplier, so any single figure can be checked with a phone calculator. The table further down is recomputed from the same expression on every build.

Bundles per square, by shingle type

One figure in the chain is not geometry at all: how much a bundle covers is whatever the manufacturer put in the wrapper. That is why the calculator takes it as an input instead of assuming 3. The common values are below — treat the last column as the authority, not this table.

Typical bundle coverage by shingle type. Coverage per bundle is 100 sq ft divided by bundles per square; confirm against the wrapper of the product you are buying.
Shingle type	Bundles per square	Coverage per bundle	Note
3-tab strip	3	≈ 33.3 sq ft	GAF lists 3 bundles per square for its Royal Sovereign 3-tab line
Standard architectural (laminate)	3	≈ 33.3 sq ft	The most common residential shingle; nearly always 3 per square
Designer / luxury	4 to 5	20 to 25 sq ft	Thicker and heavier, so more bundles per square
Oversized / metric	Check the wrapper	Varies	Metric and jumbo formats do not follow the 3-per-square rule

Bundles by plan area and pitch

Use this to sanity-check the calculator, or to order without typing anything. Read down the plan area, across to the pitch, and take the last column. The middle columns are there so you can see where the number came from: the multiplier does the slope work, and the calculated column is the multiplier applied to the plan area, times 10% waste, times 3 bundles per square.

Bundles by plan area and pitch, at 10% waste and 3 bundles per square. Bundles = plan squares × √(1 + (pitch ÷ 12)²) × 1.10 × 3, rounded up to the next whole bundle for the order column. Plan squares are the flat footprint divided by 100 — not the sloped area, and not the floor area of the house.
Plan area (squares)	Pitch	Slope multiplier	Sloped area (squares)	Bundles calculated	Bundles to order
10	3/12	1.031	10.3	34.0	35
10	4/12	1.054	10.5	34.8	35
10	5/12	1.083	10.8	35.8	36
10	6/12	1.118	11.2	36.9	37
10	8/12	1.202	12.0	39.7	40
10	10/12	1.302	13.0	43.0	43
10	12/12	1.414	14.1	46.7	47
15	3/12	1.031	15.5	51.0	52
15	4/12	1.054	15.8	52.2	53
15	5/12	1.083	16.3	53.6	54
15	6/12	1.118	16.8	55.3	56
15	8/12	1.202	18.0	59.5	60
15	10/12	1.302	19.5	64.4	65
15	12/12	1.414	21.2	70.0	71
20	3/12	1.031	20.6	68.0	69
20	4/12	1.054	21.1	69.6	70
20	5/12	1.083	21.7	71.5	72
20	6/12	1.118	22.4	73.8	74
20	8/12	1.202	24.0	79.3	80
20	10/12	1.302	26.0	85.9	86
20	12/12	1.414	28.3	93.3	94
25	3/12	1.031	25.8	85.0	86
25	4/12	1.054	26.4	87.0	87
25	5/12	1.083	27.1	89.4	90
25	6/12	1.118	28.0	92.2	93
25	8/12	1.202	30.0	99.2	100
25	10/12	1.302	32.5	107.4	108
25	12/12	1.414	35.4	116.7	117
30	3/12	1.031	30.9	102.0	103
30	4/12	1.054	31.6	104.4	105
30	5/12	1.083	32.5	107.3	108
30	6/12	1.118	33.5	110.7	111
30	8/12	1.202	36.1	119.0	119
30	10/12	1.302	39.1	128.9	129
30	12/12	1.414	42.4	140.0	141
35	3/12	1.031	36.1	119.1	120
35	4/12	1.054	36.9	121.7	122
35	5/12	1.083	37.9	125.1	126
35	6/12	1.118	39.1	129.1	130
35	8/12	1.202	42.1	138.8	139
35	10/12	1.302	45.6	150.3	151
35	12/12	1.414	49.5	163.3	164
40	3/12	1.031	41.2	136.1	137
40	4/12	1.054	42.2	139.1	140
40	5/12	1.083	43.3	143.0	143
40	6/12	1.118	44.7	147.6	148
40	8/12	1.202	48.1	158.6	159
40	10/12	1.302	52.1	171.8	172
40	12/12	1.414	56.6	186.7	187

A worked example, end to end

Take a 24 × 40 ft footprint with no overhang, a 6/12 pitch, 10% waste and 3 bundles per square. Plan area is 960 sq ft. The multiplier for 6/12 is 1.118, so the sloped area is 960 × 1.118 = 1,073 sq ft — 10.7 squares. Apply 10% waste: 11.8 squares of shingles to buy. At 3 bundles per square that is 35.4 bundles, which rounds to an order of 36.

Do it the shortcut way and you get a different answer: 960 × 1.1 ÷ 33.3 = 31.7, so 32 bundles. Four bundles short — about 130 sq ft of roof with nothing to cover it, which on a real job is a second trip to the supplier in the middle of a tear-off.

Now add the overhang. The same building with a 1 ft overhang on every side has an effective footprint of 42 × 26 = 1,092 sq ft, so the sloped area is 1,092 × 1.118 = 1,221 sq ft. That page's numbers are on the hip roof calculator, which returns the effective footprint for you; paste those two dimensions in here and the bundle count comes out at 41.

What the bundle count does not include

Field shingles are one line of a roofing order, and the one most people forget to separate from the rest:

Hip and ridge cap. A separate product, bought to the linear feet of ridge plus hips, not to the square. The hip roof calculator returns both lengths.
Starter strip. Runs along the eaves and rakes; sold by the linear foot of coverage.
Underlayment. Sold by the roll, sized to the sloped area plus laps.
Ice and water shield. Sold by the roll and applied only at eaves, valleys and penetrations.
Drip edge, flashing and vents. Linear feet and each, not bundles.

None of those change the field bundle count, and adding them to it produces the inflated orders that end with pallets going back. Size them separately.

When to let someone else order

This page does geometry and packaging arithmetic. It does not know about your local code, the wind or snow loads your roof has to meet, whether the deck needs repair, or whether the shingles you picked can legally be installed at the pitch you have — some products have a minimum slope. Steep roofs above 8/12 need more waste in practice, cut-up roofs with several valleys need more still, and a roof with a change of pitch should be split into sections and run one at a time. For anything structural, or when the total is going to be handed to a supplier as a firm order, have a roofer confirm the takeoff. The method page explains how these tables are checked before they are published.

Estimates only. These figures are geometric and packaging arithmetic, not a material takeoff and not a structural design. Spans, fastening and minimum slope must be checked against your local building code and the shingle manufacturer's published installation instructions, and structural work by a licensed engineer or contractor. Confirm bundle coverage on the wrapper before ordering.

Frequently asked questions

Why does the calculator round up to whole bundles?

Because that is the only way shingles are sold. A 24 × 40 ft footprint at 6/12 calculates to 35.4 bundles; the supplier cannot sell 35.4, and every bundle covers a fixed area printed on its wrapper. Rounding down leaves you short by part of a bundle, which on a Friday afternoon means a trip back to the yard or a stripped-in patch that will never match. Rounding up costs one bundle and leaves spares for the next repair.

How much waste should I add?

10% for a plain gable roof with two planes and no interruptions. 15% once the roof has hips, valleys, dormers, a chimney, or a change of pitch — those all create cut-offs that cannot be used elsewhere. 20% for a cut-up roof with several valleys or a lot of short runs. Waste is not padding for error: it is the material that ends up in the dumpster because a shingle cut for a valley cannot be used on a rake. On steep pitches (9/12 and up) add a couple of points on top, because more of the bundle is lost to broken and scuffed shingles as crews walk them.

Do hip and ridge cap shingles come out of the bundle count?

Usually not. Hip and ridge cap is a separate product sold by the linear foot of coverage rather than by the square of field shingles, and it is not included in the bundle figure this page calculates. To size it, add the ridge length to the four hip lengths (the hip roof calculator returns both), then buy to the coverage printed on the cap wrapper. Some architectural shingles can be cut into field-made cap, which does consume field bundles — if you plan to do that, add the cut-up allowance to the waste figure instead.

How do I work out bundles for a square or L-shaped roof?

For a square plan, nothing changes: the footprint is length × width and the slope multiplier still applies. Only the ridge and hip lengths change, and this page does not use them. For an L-shaped plan, split the footprint into rectangles at the valleys, run each rectangle through the calculator, and add the bundle counts — then round the total up, not each piece. Splitting first and rounding each piece separately over-orders by a bundle or two. Add 15% waste rather than 10% for the valleys themselves.

How much difference does the pitch actually make?

At 3/12 the slope multiplier is 1.031, so a 20-square plan works out at 68.0 bundles at 3 per square with 10% waste — order 69. At 6/12 the multiplier is 1.118 and the same plan gives 73.8, order 74. At 12/12 it is 1.414 and the figure is 93.3, order 94 — about 37% more shingles for the same footprint. That is why this page asks for pitch. The shortcut of dividing the area by 33.3 handles only the flat case, and it is wrong by up to 41% on a steep roof.