Roof replacement cost calculator
HOW MUCH DOES A NEW ROOF COST FOR MY HOUSE?
A new roof costs about $3 to $30 per square foot of roof, installed. Asphalt shingles sit at the low end and slate at the top. Enter your home below to turn that into a price range for your roof.
How the calculator works
- Roof area. Home size is divided by the number of stories to get the footprint, and any garage or porch is added. The footprint is then multiplied by a pitch factor, because a sloped roof has more surface than the floor under it. For a 6/12 pitch the factor is 1.12, which matches HomeGuide's example of a 1,000 sq ft one-story house with about 1,120 sq ft of roof.
- Price. Roof area is multiplied by the low and high installed price per square foot for your material. We show Seattle rates (Angi) and national rates (HomeGuide) side by side, because the two guides don't agree.
- Extras. Decking is priced at $2–$5 per square foot (HomeGuide) for the share of the roof you pick. Sales tax is added at Seattle's 10.55% rate if you tick the box.
| Pitch | Rise per 12 in. | Roof area factor |
|---|---|---|
| Flat or almost flat | 0–2 in. | 1.00–1.01 |
| Low | 3–4 in. | 1.03–1.05 |
| Typical | 6 in. | 1.12 |
| Steep | 8–10 in. | 1.20–1.30 |
| 45° | 12 in. | 1.41 |
Rates used
| Material | Seattle (Angi) | U.S. (HomeGuide) |
|---|---|---|
| Asphalt shingles | $3–$11 | $3–$6 |
| Flat roof (rubber, TPO) | $3–$13 | $3–$11 |
| Metal | $5–$22 | $5–$16 |
| Wood shake or cedar | $6–$18 | $7–$15 |
| Tile | — | $7–$25 |
| Slate | $10–$30 | $10–$30 |
For the full breakdown, permit rules and what to check before you sign, see our Seattle roof replacement cost guide.
Frequently asked questions
How much does a new roof cost for my house?
Multiply your roof area by the installed price per square foot for your material. Published rates run from about $3 per square foot for asphalt shingles to $30 for slate (HomeGuide, Angi). Angi puts the typical Seattle roof replacement at $8,045–$17,399, and the average Seattle roof at about 1,800 sq ft.
How do I find my roof's square footage?
Divide your home's size by the number of stories, add any garage or covered porch, and multiply by the pitch factor: about 1.05 for a low roof, 1.12 for a typical 6/12 roof and 1.41 for a 12/12 roof. A roofer's measurement will be more accurate, because it includes overhangs and dormers.
What is a roofing square?
A square is 100 square feet of roof surface. Roofers often quote per square, so a 1,800 sq ft roof is 18 squares.
Why doesn't the calculator ask for my address?
It doesn't need it. The price comes from your roof's size, pitch and material, and the math runs in your browser. Some roofing "calculators" we have seen in ads ask for your address and phone number first, because they collect leads for roofing companies. This one sends nothing anywhere.
Sources
- Angi — How Much Does Roof Replacement Cost in Seattle, WA? (updated Aug 4, 2026)
- HomeGuide — Roof Replacement Cost (edited Nov 7, 2025)
- Washington Department of Revenue — Local sales tax change, Seattle, effective January 1, 2026
- Washington Department of Revenue — Custom construction
All sources accessed September 27, 2026.
This calculator gives a rough range from published average rates. It is not a quote and can't see your roof. Nothing you enter is sent anywhere or stored. Get written estimates from licensed, bonded and insured roofers before deciding. See our disclosure and disclaimer.