The answer
Roofing is calculated in squares (1 square = 100 sq ft). Installed costs: 3-Tab: $350–$500/sq ($3.50–$5.00/sq ft); Architectural Shingles: $450–$800/sq ($4.50–$8.00/sq ft); Metal: $700–$1,600/sq; Tile: $800–$1,800+/sq; Flat/Low-Slope: $450–$1,000/sq. Cost multipliers include pitch steepness, complex geometry, layer tear-offs, and decking plywood replacement.
Sources
This answer is drawn from the standards and guidance below. It is general information about how these systems work — not a diagnosis of your property.