Roofing Squares & Bundle Calculator

Pitch makes the real (sloped) roof bigger than its flat footprint. We apply the standard slope factor, surface it in the result so you can trust the correction, convert the corrected area to roofing squares (1 square = 100 ft²), add your waste allowance, and round up to whole bundles only at the very last step.

multiplier   = √(rise² + 12²) / 12        (rise:12 pitch; 0/12 = 1.0)
roof_area    = footprint_ft² × multiplier
squares      = roof_area / 100            (kept as a decimal)
squares_adj  = squares × (1 + waste%)
bundles      = ceil(squares_adj × bundles_per_square)
shingles     = bundles × 29
companion (optional):
  felt_rolls = ceil(roof_area / 400)      (15# felt; 200 for 30#)
  nails      = round(squares × 320)       (3-tab)
cost (optional):
  material   = squares_adj × price_per_square

Worked example — 50 ft × 30 ft footprint (1,500 ft²) at 6/12 with 10% waste and 3 bundles/square: multiplier ×1.1180, roof area ≈ 1,677 ft², ≈ 16.77 squares → ≈ 18.45 with waste → 56 bundles and 1,624 shingles. Bundles come from the un-rounded adjusted squares, not a re-rounded square count — which prevents the common off-by-a-bundle error.

Defaults reflect standard architectural asphalt shingles (3 bundles/square, 29 shingles/bundle) and US 2026 conventions from Omni Calculator and Inch Calculator. This is an estimate and an ordering aid — verify quantities against your roof and supplier before ordering.

A bundle count is a material order, not a price. Turning it into one means adding labor, tear-off, overhead and markup, which the trade-neutral cost build-up handles for any trade, with the markup step itself explained in a side-by-side of the two percentages.

The quantities here drop into the roofing estimate template for a steep-slope job, or the TPO commercial roofing estimate template when the deck is flat and the material is membrane. Anyone working at that height should also be carrying the job site safety inspection checklist, and a shop planning a season of roofs writes it up in the roofing business plan template.

Formula: multiplier = √(rise² + 12²) / 12 · squares = roof ft² / 100 · bundles = ⌈squares × (1+waste) × bundles/sq⌉

See Sources below ↓