ShingleTallySquares, bundles and everything else a roof needs, counted properly.

Shingles for a 34 × 36 ft roof at 10/12, simple gable

Shingles
53bundles
17.5 squares for a 34 × 36 ft footprint at 10/12 — simple gable, 10% waste
Footprint34 ft36 ft1,224 ft²×1.3021,593 ft²of actual roof17.5 squares53 bundles · 10% waste+3.7 squaresthat footprint alone misses
Bundles3 per square53bundles
Squares (with waste)17.5sq
Roof area1,224 ft² footprint × 1.302 pitch factor1,593ft²
Pitch factor√(1 + (10/12)²) — pure geometry1.302
Waste allowancetwo planes, cuts only at the rakes10%
Starter shingles140 ft of eave and rake2bundles
Hip & ridge cap36 ft of ridge2bundles
Underlaymentsynthetic, 10 squares per roll2rolls
Ice & water shieldeaves, 24″ inside the exterior wall line — check if your code requires it547ft²
Roofing nails — standard4 per shingle, about 5,608 nails41lb
Roofing nails — high wind6 per shingle — required in high-wind zones and by most warranties above 110 mph61lb
Walkable10/12 is past the point most people can stand onNo — staging needed
Footprint width
34 ft
Footprint length
36 ft
Pitch
10 /12
Roof type
simple gable

Footprint is not roof area

This is where roofing estimates go wrong, and they go wrong in the direction that leaves you short on a Saturday.

A 34 × 36 ft footprint is 1,224 ft² on the ground. At 10/12 the roof over it is 1,593 ft² — the pitch factor is 1.302, which is √(1 + (10/12)²). Pure geometry, no fudge factor.

Order off the footprint and you are 3.7 squares short before waste is even counted.

Squares and bundles

17.5 squares with 10% waste for a simple gable roof — 53 bundles at three per square.

Waste is not one number. A simple gable cuts only at the rakes. A hip roof cuts along every hip. A cut-up roof with valleys and dormers throws away a fifth of what you buy, and no amount of careful planning changes that.

The two lines everyone forgets

Starter: 2 bundles for 140 ft of eave and rake. Hip and ridge cap: 2 bundles for 36 ft.

These are separate products, not field shingles cut down. Using field shingles as starter voids most manufacturers' wind warranties, which is discovered at the claim rather than at the purchase.

Underneath

2 rolls of synthetic underlayment, and 547 ft² of ice-and-water shield at the eaves — 24 inches inside the exterior wall line, which is what the IRC asks for where it applies. Check whether your jurisdiction requires it.

41 lb of roofing nails at four per shingle, or lb at six for a high-wind zone.

Two things to price before you decide it is DIY

Tear-off: about 4,820 lb of old shingle to strip and skip.

And access. Above 8/12 a roof stops being walkable for most people, and roof jacks, planks or scaffolding cost real money that belongs in the estimate before you decide this is a DIY job.

Notes

  • **Footprint is not roof area, and the gap is bigger than people expect.** A 34 × 36 ft footprint is 1,224 ft² on the ground but **1,593 ft²** of roof at 10/12. Ordering off the footprint leaves you 3.7 squares short — and that is before waste.
  • The pitch factor is √(1 + (rise/12)²). There is no estimate in it and no manufacturer fudge — it is the hypotenuse. 10/12 gives 1.302.
  • 10% waste for a simple gable roof: two planes, cuts only at the rakes. A simple gable wastes least because the only cuts are at the rakes; every hip and valley adds a run of angled cuts that produce offcuts nothing else uses.
  • Starter and cap are separate purchases, and they are the two lines that get left off estimates. 2 bundles of starter for 140 ft of eave and rake, 2 bundles of hip and ridge for 36 ft. Using field shingles as starter voids most manufacturer wind warranties.
  • At 10/12 this is not a walkable roof for most people. Roof jacks and planks, or scaffolding — and that cost belongs in the estimate before you decide whether this is a DIY job.
  • Tear-off is the other half of the job. A single layer of asphalt shingle weighs 200–350 lb per square, so this roof carries about 4,820 lb of old material to remove and skip.

Nearby sizes

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