Tap & Trowel Home-project calculators & repair guides

Shingle calculator

Enter the sloped roof area, or the plan footprint and a pitch, plus a waste allowance. You'll get roofing squares and asphalt shingle bundles (typically 3 per square — check the wrapper). Optional price per bundle estimates material cost. Defaults are a 2,000 ft² roof surface with 10% waste.

By Jordan Hale · Updated

Units
Measure by
Sloped faces, not the house footprint. Include overhangs.
GAF often suggests about 10–15% for trim and waste. Use more for hips, valleys and dormers.
Optional: estimate material cost

Use your supplier's price per bundle. Nothing is pre-filled.

You need about

Bundles
–
Squares (with waste)
–
Roof area (ft²)
–
Pitch multiplier used
–
Material cost
–

One square = 100 ft² (GAF). Bundles are rounded up. Starter strip, ridge cap, underlayment and nails are separate—confirm coverage on each product's label.

Illustration of asphalt shingles being laid on a roof deck, with a bundle of shingles, a roofing hatchet and a chalk line on the sheathing.
Illustration

How the calculator works

  1. Roof area: use the sloped surface area, or multiply plan area by the pitch multiplier from the roof pitch calculator (√(1 + (rise/run)²)).
  2. Squares: area ÷ 100, then add your waste percent. GAF defines a square as 10 × 10 ft (100 ft²).
  3. Bundles: squares × bundles per square, rounded up. GAF says most standard asphalt shingles (including Timberline HDZ) come three bundles per square; some specialty lines need four or five. Always read the wrapper.
  4. Cost: bundles × your price per bundle, if entered.

Waste and complexity

GAF recommends adding about 10–15% for trim allowance and waste when converting area to material. Simple gables often sit near 10%; hips, valleys, dormers and steep cuts push toward 15% or more. There is no single code waste factor—ask your supplier or roofer for a cut-up roof.

Pitch limits for asphalt shingles

The IRC (R905.2.2) allows asphalt shingles only on slopes of 2:12 or greater. From 2:12 up to 4:12, double underlayment (or an approved self-adhering underlayment) is required; at 4:12 and steeper, a single layer is the usual IRC path. Manufacturer instructions can be stricter. See the roof pitch calculator for rise/run, degrees and multiplier.

Fall protection (OSHA)
  • OSHA requires fall protection for residential construction work 6 feet or more above a lower level (29 CFR 1926.501(b)(13)): typically guardrails, safety nets or a personal fall arrest system, unless another Subpart M provision applies.
  • On steep roofs (more than 4:12), roofing work at 6 feet or more needs guardrails with toeboards, nets or personal fall arrest (1926.501(b)(11)). Low-slope roofs (4:12 or less) have additional options under 1926.501(b)(10), such as warning lines with a monitor in some cases.
  • Homeowners doing their own roofing still face the same fall hazards. Use a secure ladder, non-slip footwear and proper fall protection for the pitch and height. Ice, dew and granules make steep decks slick. If you are unsure, hire a licensed roofing contractor.

Related: roof pitch calculator, square footage calculator, roof replacement cost, metal roof cost, gutter replacement cost. For other project costs, see the cost guides.

Sources

How this page was made. Jordan Hale is the author and is responsible for this page. An AI assistant helped write the code, gather manufacturer data and draft the explanation. The math is covered by automated tests against the published reference values cited below. The calculator gives a planning estimate. It does not replace the product label, your supplier or an engineer. The illustration on this page is AI-generated and shows the general idea, not exact construction details.