Shingle Calculator: Bundles, Starter & Ridge Cap

Bundles of shingles for your roof from its size and pitch, with the starter strip and ridge cap from the same maker.

By Marko VisicBSc Physics, University of LjubljanaUpdated Nov 14, 2026

51bundles

bundles of GAF Timberline HDZ, 10% waste included

15.03 squares of roof, 32.8 sq ft a bundle

Dashed: eaves and rakes, where the starter strip goes. Heavy: ridge and hips, where the cap goes.

Roof area: 1,503 sq ft
Bundles before waste: 46
Coverage per bundle: 32.8 sq ft
Starter strip: 2 bundles
Ridge cap: 3 bundles
Squares of roof: 15.03

Starter: 156 ft of eaves and rakes, GAF Pro-Start at 120.33 lin ft a bundle: 2 bundles
Ridge cap: 42 ft of ridge and hips, GAF TimberTex at 20 lin ft a bundle: 3 bundles

GAF Timberline HDZ: 3 bundles to the square, rated at 98.4 sq ft per square, where a roofing square is 100 sq ft. GAF says contractors usually add 10–15% for waste. Why the counts differ by brand: how many bundles of shingles in a square.

Roof size

Units

Length (ft)

Width (ft)

Overhang, each side (in)

Roof pitch

Roof shape

Shingle line

Waste allowance

51 bundles of GAF Timberline HDZ, plus 2 bundles of starter and 3 bundles of ridge cap

Divide the roof area by what one bundle covers and add waste. A 40 by 30 ft gable with 1 ft overhangs at 6/12 takes 51 bundles of GAF Timberline HDZ with 10% waste, plus 2 bundles of starter for 156 ft of eaves and rakes and 3 of ridge cap for its 42 ft ridge.

Each shingle line rates its bundles for its own coverage, and many laminated lines cover a little less than a full square in three bundles, so the calculator works from the coverage of the line you pick rather than a flat three bundles per square.

How to calculate shingles for a roof

Find the roof’s surface, add the waste allowance, and divide by the coverage of one bundle of the shingle you are buying. Round up: you buy whole bundles. A roofing square is 100 square feet, but the bundles sold as a square are rated for their own coverage, which the wrapper states.

Roof area = (length + 2 × overhang) × (width + 2 × overhang) × pitch multiplier

Bundles = roof area × (1 + waste) ÷ coverage per bundle, rounded up

Coverage per bundle = rated coverage per square ÷ bundles per square

Example: the 42 by 32 ft footprint is 1,344 sq ft; times the 6/12 multiplier of 1.118 that is 1,502.6 sq ft of roof. Timberline HDZ covers 32.8 sq ft a bundle, so the roof takes 46 bundles before waste, 51 with 10% and 53 with 15%.

GAF says contractors usually add 10–15% for waste; the calculator offers both ends. The count covers the field of the roof; starter and cap are counted separately below.

How to measure a roof for shingles

You can do it from the ground. Measure the outside walls with a tape, then stand under an eave and measure from the wall to the roof edge for the overhang. The pitch is the one figure that comes from the roof itself, and the roof pitch calculator finds it from a level reading, an angle or the building’s width and ridge height.

A hip roof is measured the same way: its area over the same eaves and pitch equals a gable’s. For a roof with parts at different pitches, such as a porch, work each part separately in the roof square footage calculator, add the areas, and enter the total with the “I know the roof area” option.

Figuring starter strip and ridge cap

Starter strip runs along the edges where the shingles start: GAF’s Pro-Start installs at the eaves and rakes, and Owens Corning’s Starter Strip Plus gives a straight edge at the eave and along the rake. Cap shingles cover the ridge and the hips. Both are sold by the lineal foot of edge they cover.

Coverage per bundle, or per carton for DecoRidge and Berkshire Hip & Ridge.
Product	Use	Covers per package
GAF Pro-Start	Starter	120.33 lin ft
Owens Corning Starter Strip Plus	Starter	105 lin ft
CertainTeed SwiftStart	Starter	116.25 lin ft
GAF TimberTex	Hip and ridge	20 lin ft
GAF Seal-A-Ridge	Hip and ridge	25 lin ft
Owens Corning ProEdge	Hip and ridge	33 lin ft
Owens Corning DecoRidge	Hip and ridge	20 lin ft
Owens Corning Berkshire Hip & Ridge	Hip and ridge	20 lin ft
CertainTeed Shadow Ridge	Hip and ridge	30 lin ft

Rakes and hips run along the slope, so they are longer than they look in plan. On the example house each rake is 17.9 ft (half the 32-foot width times the multiplier); as a hip roof, each hip would be 24.0 ft, since a hip also runs diagonally across the plan.

Gable, hip and shed roofs

Over the same eaves and at the same pitch, all three shapes have the same roof area and take the same shingle bundles. What changes is the edges: a gable has two eaves, four rakes and a ridge; a hip has eaves all round, a shorter ridge and four hips; a shed has one eave, two rakes and a high edge with no ridge, so the calculator counts no cap there.

The 42 by 32 ft example at 6/12 with 10% waste.
Roof shape	Starter edges	Starter bundles	Ridge and hips	Cap bundles	Shingle bundles
Gable	156 ft	2	42 ft	3	51
Hip	148 ft	2	106 ft	6	51
Shed	114 ft	1	0 ft	0	51

Shingle calculator FAQ

How many roof shingles do I need?

Divide the roof’s surface by what one bundle covers, then add waste. GAF Timberline HDZ covers about 32.8 sq ft a bundle, so 2,000 sq ft of roof takes 68 to 71 bundles with the 10–15% waste GAF says contractors usually add.

How do I calculate shingles for a hip roof?

The same way as a gable: a hip over the same eaves at the same pitch has the same roof area, so it takes the same bundles of shingles. It needs more ridge cap, because the four hips are capped as well as the ridge, and no rake starter, since every edge is an eave.

How do I calculate starter shingles?

Add the lengths of the eaves and the rakes and divide by the starter’s coverage per bundle: about 120.33 lin ft for GAF Pro-Start, about 105 for Owens Corning Starter Strip Plus and 116¼ for CertainTeed SwiftStart. Round up to whole bundles.

How do I figure ridge cap shingles?

Measure the ridge and every hip along the roof, add them, and divide by the cap’s coverage per bundle. GAF says a bundle of hip and ridge caps covers 20 to 33 lineal feet depending on the type: 20 lin ft for TimberTex, 33 ft for Owens Corning ProEdge.

Does a steeper roof need more shingles?

Yes, over the same footprint. The roof grows by the pitch multiplier: at 6/12 it is 11.8% larger than flat and at 12/12 about 41% larger, so the bundle count rises by the same share.

Sources & method

Roof area is the footprint to the eaves times the pitch multiplier √(1 + (pitch ÷ 12)²). Bundles are the area plus waste divided by the line’s coverage per bundle (rated coverage per square ÷ bundles per square; for GAF lines, shingles × length × exposure ÷ 144), rounded up. Rakes are half the width × the multiplier, hips half the width × √(2 + (pitch ÷ 12)²); starter and cap are those lengths divided by each product’s published coverage, rounded up. Coverage figures are from each maker’s data sheets.

GAF. Timberline HDZ Shingles Spec Sheet. RESGN467HDZ-0526
Owens Corning. TruDefinition Duration Shingles data sheet. Pub. No. 10013984-L (December 2022)
GAF. About Royal Sovereign Shingles (product page, specifications). page read Nov 14, 2026
Owens Corning. TruDefinition Duration MAX Shingles product data. Pub. No. 10022486-I (March 2026)
Owens Corning. Berkshire Shingles product data. Pub. No. 10003277-N (October 2023)
Owens Corning. Starter Strip Plus Shingle (product page). page read Nov 14, 2026
GAF. All About Hip and Ridge Cap Shingles. Sep 21, 2023
Owens Corning. ProEdge Hip & Ridge Shingles brochure. Pub. No. 10016668-P (September 2020)
GAF. How Many Bundles of Shingles Are in a Square? (Quick Answer + Calculator). Aug 24, 2026
Owens Corning. DIY Roofing: Re-Roofing Tips (What is a “Roofing Square”?). page read Nov 14, 2026

How Many Bundles of Shingles in a Square? Counts by BrandBundles, shingles and coverage per square from the makers’ spec sheets.
Roof Square Footage Calculator: Area & Roofing SquaresRoof surface and roofing squares from the footprint, overhang and pitch.
Roof Pitch Calculator: Degrees, Slope & Roof HeightFind the pitch from a rise and run, an angle or a building’s width.