CONSTRUCTION · ROOFING

Roof Replacement Calculator

Estimate the roofing squares, shingle bundles, and total cost for your roof replacement. Adjusts for roof pitch and compares asphalt, metal, tile, and slate options.

LAST REVIEWED · APR 24, 2026 · BY D. MARQUEZ, P.E.
You need
23.2 squares
Est. cost
$10,435
Roof DetailsReset
Footprint areaBuilding footprint
sq ft
Roof pitchRise per 12" run
Roofing material
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How the roof replacement calculator works

You don't need to climb on the roof to estimate materials. Enter the building footprint area (length × width as seen from above) and the roof pitch. The calculator applies a pitch multiplier to compute actual roof area, then converts to roofing squares (1 square = 100 sq ft).

Understanding roof pitch

Pitch is expressed as rise/12 — a 4/12 pitch rises 4 inches for every 12 inches of horizontal run. Steeper roofs use more material because they cover a larger actual area than the flat footprint suggests.

  • Low pitch (2–4/12) — ranch homes, modern architecture
  • Medium pitch (5–8/12) — most residential homes
  • Steep pitch (9–12/12) — colonial, Tudor, Victorian styles

Roofing material costs

  • 3-tab asphalt — $350/square, 20-year warranty
  • Architectural asphalt — $450/square, 30-year warranty
  • Standing seam metal — $800/square, 50+ year lifespan
  • Concrete tile — $1,200/square, 50+ year lifespan
  • Natural slate — $1,800/square, 100+ year lifespan
Methodology. Roof area = Footprint area × Pitch multiplier. Squares = Roof area ÷ 100. Bundles = Squares × 3 (asphalt shingles). Pitch multipliers from 0/12 (1.000) to 12/12 (1.414). Includes a 10% waste factor for hips, valleys, and starter courses.

Sources

  • NRCA (National Roofing Contractors Association) guidelines
  • Roof pitch multiplier table: √(1 + (pitch/12)²)
  • Average roofing costs: $350–$1,800/square depending on material (2026)
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Frequently asked questions

How many squares is my roof? +
Measure your home's footprint (length × width from the outside) and multiply by the pitch factor. A 2,000 sq ft footprint with a 4/12 pitch: 2,000 × 1.054 = 2,108 sq ft ÷ 100 = 21.1 squares.
How many bundles of shingles per square? +
Standard asphalt shingles require 3 bundles per square. With a 10% waste factor for a 21-square roof, you'd need about 23 squares × 3 = 69 bundles.
Should I tear off old shingles or go over them? +
Most codes allow one layer of overlay. Tearing off adds $1–$2/sq ft but lets you inspect the decking for damage and provides a cleaner installation. If you already have two layers, tear-off is required.
How long does a roof replacement take? +
A typical residential roof (20–30 squares) takes 1–3 days for a professional crew. Tear-off adds about half a day. Weather delays and complex roof shapes (dormers, multiple valleys) extend the timeline.
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