Understanding your result
The headline is the number of starter bundles. The stats show the total edge to cover before waste, the approximate number of pieces and the nails. The breakdown separates eaves from rakes, so if the rake line is the one that pushed you into a second bundle, you can see it.
The number to remember is the edge to cover: eaves plus rakes. It is the same length the drip edge calculator uses, because drip edge goes on every edge the starter does, and it is the eave part of it that the ice and water shield calculator starts from. Measure it once and use it three times.
When the order lands just over a whole number of bundles, the result says so. A bundle and a few feet is a real order of two bundles, but it is worth re-measuring before paying for a bundle you will use a tenth of.
How we calculate this
The only step that needs a word is the coverage of cut three-tab shingles. A three-tab shingle is 36 inches wide; cutting off the tabs leaves a strip the full 36 inches long, and a bundle holds about 26 shingles, so a bundle gives 78 feet of starter. Purpose-made starter is a thinner strip packaged to cover more, typically 100 to 120 feet. Either way the strip must be laid with its sealant line at the eave, which is the one detail that decides whether the first course seals.
The piece count assumes starter pieces about 39 inches long, which is the common size for purpose-made strips; cut three-tab pieces are 36 inches, so the count is a little higher but the nails, at five per piece, come out almost the same.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Coverage per starter bundle | 105 linear ft | Typical of purpose-made starter products (manufacturers’ data sheets state 100 to 120 ft); the bundle wrapper is the authority |
| Shingles per three-tab bundle | 26 | Manufacturers’ bundle counts for standard three-tab shingles (26 to 27) |
| Strip length from a three-tab shingle | 36 in | The standard three-tab shingle width |
| Starter piece length | 39 in | Common size of purpose-made starter strips; used for the piece and nail count |
| Nails per piece | 5 | Manufacturers’ starter instructions (4 to 5 nails, 2 to 3 in above the eave edge) |
| Waste | 5% | Estimating practice for a linear material cut at corners and ends |
Assumptions last reviewed October 7, 2026.
The calculator does not model starter around dormers and porch roofs unless you add their eaves and rakes to the totals, and it does not know your product’s exact coverage: a bundle that covers 120 feet rather than 105 can save a bundle on a large roof. The guide to drip edge, flashing and the eave details shows where the starter sits relative to the drip edge and the ice barrier.
Two worked examples
A gable house with starter on the rakes
Two 40-foot eaves and four 18-foot rakes, purpose-made starter at 105 feet per bundle, 5% waste.
- Edge to cover: 80 + 72 = 152 ft
- With waste: 152 × 1.05 = 159.6 ft
- Bundles: 159.6 ÷ 105 = 1.52, rounded up to 2 bundles
- Pieces: 159.6 × 12 ÷ 39 = 49.1, so 50 pieces
- Nails: 50 × 5 = 250
Two bundles, with almost half a bundle left over. If the product covers 120 feet, the order is still two bundles, because 160 feet is more than one.
A hip roof with eaves only, cut three-tab starter
A hip roof has no rakes. Its eaves total 140 feet, and the roofer cuts starter from three-tab shingles, 26 to the bundle.
- Edge to cover: 140 ft
- With waste: 140 × 1.05 = 147 ft
- Coverage per bundle: 26 × 3 = 78 ft
- Bundles: 147 ÷ 78 = 1.88, rounded up to 2 bundles
- Pieces: 46, nails: 230
Two bundles of three-tab shingles cover it, with the tabs cut off to use as cap on a three-tab roof. On an architectural roof, buy purpose-made starter and cap instead; the ridge cap calculator prices the cap.
Where to find your inputs
Eave length. The horizontal bottom edges of every roof plane, including porches and dormers. On a gable roof that is twice the house length plus the rake overhangs; on a hip roof it is the whole perimeter at the drip edge.
Rake length. The sloped edges at each gable end. Each rake is half the house width plus the overhang, multiplied by the pitch factor; the rafter length calculator gives it exactly, or measure a rake board from the ground with the method in the measuring guide.
Coverage per bundle. On the wrapper of the starter product, usually as “covers X linear feet”. If you are between products, 105 feet is a fair middle figure.
Common mistakes
- Leaving out the rakes. The rake edge is where wind lifts shingles first, and the warranty on many products depends on starter there. Tick the box unless the manufacturer says otherwise.
- Laying the sealant strip up the slope. The adhesive line must sit at the eave edge to glue down the first course. Cut starter from three-tab shingles is laid upside down relative to a normal course for exactly this reason.
- Lining up starter joints with first-course joints. Offset them by at least 6 inches; a joint over a joint is a path straight to the deck.
- Cutting architectural shingles for starter. Their sealant line is in the wrong place and the strip is too thick to lie flat. Use purpose-made starter.
- Flush with the drip edge. Starter should overhang the drip edge by ¼ to ¾ in so water drips clear of the fascia instead of running back along it.
- Forgetting the dormers. Each dormer roof has its own eaves and rakes. Add them to the totals, or the last dormer gets no starter.
Questions people ask
- What is a starter strip for?
- The first course of shingles has gaps between its tabs or its cut-outs, and the joints between shingles would otherwise sit over bare underlayment. The starter course underneath seals those gaps with a continuous strip whose adhesive line sits at the eave, so wind cannot lift the first course and water cannot reach the deck through the joints.
- How many feet does a bundle of starter cover?
- Purpose-made starter bundles typically cover 100 to 120 linear feet; the figure is printed on the wrapper and the calculator's default is 105 feet. A bundle of three-tab shingles with the tabs cut off gives about 26 strips of 36 inches, roughly 78 feet. The calculator's example roof with 152 feet of eaves and rakes needs two bundles of either kind.
- Do I need starter strip on the rakes?
- Most manufacturers recommend it and some require it for their wind warranty, because the rake edge is where wind gets under the shingles first. On a plain gable roof the rakes add about as much length as the eaves: a 40 by 30 foot house at 6/12 has 80 feet of eaves and about 72 feet of rakes.
- Can I use regular shingles as starter?
- Three-tab shingles with the tabs cut off work, provided the sealant strip ends up along the eave edge, which means turning the shingle so the adhesive line faces down the slope. Architectural shingles should not be cut for starter; their sealant line is in the wrong place and the strip is too thick.
- How far should starter overhang the drip edge?
- A quarter to three-quarters of an inch beyond the drip edge at both eaves and rakes, so water drips clear of the fascia. The joints of the starter course must be offset from the joints of the first course by at least 6 inches, which is why the calculator adds 5% waste for cuts.
- How many nails does a starter course take?
- Four to five nails per piece, placed 2 to 3 inches up from the eave edge and above the sealant strip. A 39-inch starter piece every 3¼ feet along 160 feet of edge is about 50 pieces and 250 nails, a small fraction of the roof's nails; the roofing nails calculator adds 10% to the field count to cover starter, caps and flashing.