How the roof replacement cost calculator works
The cost stack
Architectural shingle roofs run $4.50–9.00 per sq ft installed depending on region, tier, and roof difficulty — tear-off adds $1.25–2.25 per sq ft per layer. Two stories and steep pitches multiply labor (staging, safety, pace). The per-square installed number is the only comparable currency between quotes.
Reading the quote line by line
Legitimate quotes itemize: tear-off, underlayment (synthetic + ice shield in cold climates), drip edge, shingles by bundle, ridge venting, pipe boots and flashing, dumpster, and permits. Vague single-number quotes hide the substitutions — underlayment and flashing are where cheap roofs quietly become cheap roofs.
When repair beats replacement
Under ~10 years old with localized damage (wind-lifted shingles, one flashing failure), repair wins. Past 70–80% of expected life (20–30 years for architectural), replacement economics win — repair costs compound and the second reroof never gets cheaper. The honest trigger is usually the second repair call in two years.