How the calculator works
A roof is priced by its surface, not by the floor area of the house. So the estimate starts by turning your footprint into roof area, then multiplies it by a price per square foot for the material you picked, and adds the cost of removing the old roof.
Roof area = footprint x 1.10 (overhangs) x pitch factor. Cost = roof area x material price x labor factors + roof area x tear-off price x layers
A 2,000 square foot single-story home with a 6/12 pitch has 2,000 x 1.10 x 1.118 = about 2,460 square feet of roof, or 24.6 squares. In architectural shingles at $4.75 to $7.50 per square foot on an average-shaped roof, plus one layer of tear-off at $1 to $2, that is roughly $15,300 to $25,200.
Roof pitch and why it matters
Pitch is the rise in inches for every 12 inches across. A steeper roof covers the same footprint with more surface, so it needs more material:
| Pitch | Multiply footprint by | Walkable? |
|---|---|---|
| Flat to 2/12 | 1.00 to 1.01 | Yes |
| 4/12 | 1.054 | Yes |
| 6/12 | 1.118 | Yes, most common |
| 8/12 | 1.202 | With care; harnesses often required |
| 10/12 | 1.302 | No, needs roof jacks and staging |
| 12/12 | 1.414 | No |
To find your pitch without climbing up, hold a level horizontally against a gable end from a ladder, measure 12 inches along it and then measure straight up to the roof edge. That number is the rise.
Cost by roofing material
Typical installed prices in the United States, including underlayment, standard flashing and labor:
| Material | Per sq ft installed | Typical life |
|---|---|---|
| 3-tab asphalt shingles | $4.00 to $5.50 | 15 to 20 years |
| Architectural asphalt shingles | $4.75 to $7.50 | 25 to 30 years |
| Corrugated metal | $6 to $10 | 25 to 40 years |
| Flat roof membrane (TPO, EPDM) | $6 to $11 | 20 to 30 years |
| Wood shakes | $8 to $14 | 25 to 30 years |
| Concrete or clay tile | $9 to $20 | 50 years or more |
| Standing seam metal | $10 to $16 | 40 to 70 years |
Architectural shingles are the default choice for most homes: thicker than 3-tab, better wind ratings and a longer warranty for a modest premium. Metal and tile cost more up front but can outlast two or three shingle roofs.
Costs the estimate cannot see
- Rotten decking. Soft plywood or OSB found during tear-off is replaced at $70 to $120 per sheet. Keep about 10 percent of the budget for it.
- Permits. Most towns require one for a full replacement, usually a few hundred dollars.
- Chimneys, skylights and walls. New flashing around each one adds labor and material.
- Ventilation. Ridge vents or extra intake vents may be needed for the shingle warranty to apply.
- Gutters. Old gutters often come off during the job; replacing them at the same time saves a second setup.
Comparing roofing quotes
Ask every roofer to quote the same scope so the prices are comparable: the number of squares, the exact shingle line, full tear-off, ice and water shield in valleys and at the eaves, drip edge, ventilation, decking price per sheet and the warranty. Manufacturer-certified contractors, such as GAF certified roofers, can register enhanced warranties that cover labor as well as materials.
A quote far below the others usually leaves something out: an overlay instead of a tear-off, no underlayment upgrade, or decking not included. Check what is missing before choosing on price alone. Roofing contractors on ProBusiness101 list their services and service areas, so you can shortlist two or three local roofers before you ask for quotes.