Roofing · US units

Roofing Calculator — Squares and Bundles

GAF Timberline HDZ ships 3 bundles per square. A square is 100 sq ft of sloped roof, not living area. Pitch factor is √(1 + (rise/12)²); default 4/12 is 1.054. The 10% toggle is a labelled convention on field area. It is not GAF starter-strip, hip, or ridge math.

Basket 2026-08-27

Footprint and pitch

Bundles to buy

42 bundles

41.742 exact · 13.91 squares · 3 bundles/sq

Cost: enter a local price to see a dollar total. We will not invent one.

Plan footprint: 1,200 sq ft
Pitch factor: 1.054
Sloped surface: 1,264.9 sq ft
After 10% labelled waste: 1,391.4 sq ft
Squares (100 sq ft): 13.914

Timberline HDZ is 3 bundles per 100 sq ft square. Starter, hip, and ridge are not in this count.

What calculator.net does not show

Many roof widgets pad squares for starter, hip, and ridge inside the same bundle count and call it “GAF waste.” Those are separate SKUs. This page multiplies plan footprint by the pitch factor, divides by 100, multiplies by 3, then optionally adds a labelled 10%. Bundle dollars start empty — HDZ pricing is zip-localized.

If you already taped every sloped plane, do not apply the pitch factor again. This slug is /roofing-calculator, not a “squares” clone URL.

Worked US example: 30×40 footprint, 4/12

Simple rectangle, 10% labelled waste, Timberline HDZ 3 bundles/square.

Plan          = 30 × 40 = 1,200 sq ft
Pitch factor  = √(1 + (4/12)²) = 1.054
Sloped        = 1,200 × 1.054 = 1,264.91 sq ft
10% labelled  = 1,264.91 × 1.10 = 1,391.40 sq ft
Squares       = 1,391.40 ÷ 100 = 13.914
Bundles       = 13.914 × 3 = 41.742 → buy 42 bundles
Cost          = $ null until you type a local bundle price
(no starter / hip / ridge extras in this count)

Citations

GAF. Timberline HDZ shingles — bundles per square. Accessed 2026-08-27. https://www.gaf.com/en-us/roofing-materials/residential-roofing-materials/shingles/timberline-hdz — Specifications: 3 bundles per square, 64 pieces per square, 5-5/8 in exposure. A roofing square is 100 sq ft of sloped roof surface. This calculator does not add GAF starter-strip, hip, or ridge extras — waste is a labelled 10% convention on the field area only.

These calculators estimate material takeoff for planning. They are not engineering, structural, or code advice. Confirm spans, mixes, fastener schedules, and permits with a licensed professional and the manufacturer’s current data sheet. Local shelf prices and tax are not this index.