How many bundles of shingles cover one square?

Three bundles per square for common architectural shingles; one square is 100 sq ft of roof surface. Some heavier premium lines pack four or five bundles to the square; the wrapper states the coverage.

How much waste should I allow?

Ten percent on a simple gable roof, fifteen percent or more once hips, valleys and dormers multiply the cuts. Valleys and hips consume shingles in offcuts that a flat plane never sees.

Does this tell me what my roof will cost?

No, it counts material. For a San Antonio installed-cost range, use the roof replacement cost calculator, which prices squares rather than counting bundles.

What else does a shingle roof need besides shingles?

Underlayment across the whole deck, starter strip at eaves and rakes, hip and ridge caps, drip edge, and ice-and-water membrane in valleys and around penetrations. The calculator counts underlayment; the rest is bought by linear foot.

Shinglecalculator

Footprint and pitch in; squares, bundles, underlayment and waste out. It is the same arithmetic a supplier's counter runs, shown in full so you can check a materials line instead of taking it on faith.

Architectural asphalt shingles photographed flat, showing the layered tab pattern. — Architectural asphalt shingle

Shingle calculator

The working

Roof surface: not set
With waste: not set
Roofing squares: not set
Shingle bundles: not set
Underlayment rolls: not set

3 bundles per square (architectural shingle); one synthetic underlayment roll covers about 10 squares. For dollars, use the cost calculator.

Checking a materials line without climbing a ladder

A roofing estimate's material count should reconcile with this arithmetic to within a bundle or two. When it doesn't, ask why; there is often a good answer, and it should be a specific one.

Squares are the trade's unit

Every San Antonio roofing estimate prices in squares: 100 sq ft of roof surface. A 1,800 sq ft single-storey home at a 6/12 pitch carries about 20 squares before waste, which is why “a 20-square roof” is shorthand for an ordinary suburban replacement.

Where the waste number comes from

Every valley and hip line consumes shingles as angled offcuts, and starter courses double the first row at eaves and rakes. A plain gable wastes about a bundle in ten; a cut-up roof with dormers can waste one in five. An estimate that carries zero waste is not sharper; it is a change order waiting for week two.

The parts this page doesn't count

Starter strip, ridge caps, drip edge, and the ice-and-water membrane that belongs in every valley are bought by linear foot, not by square, so they need a tape measure rather than a footprint. They are real money on a small roof and rounding error on a big one.

Rather have a crew count it?

Want to talk to a specific ranked company instead? Every listed company’s own phone number is on their profile.