Roof replacement cost calculator

The installed price covers the roofing, underlayment, flashing, labor and the roofer's margin. These are the ranges the calculator uses, combined from the cost guides listed under the calculator. Low is the average of the guides' lows, high the average of their highs, and typical sits in the middle.

Tear-off is extra: about $0.75 to $3.25 a sq ft for each layer, disposal included. HomeAdvisor adds $1,000 to $3,000 for roofs at 9/12 and steeper, where crews need roof jacks and harnesses and move slower.

For a whole house, HomeAdvisor puts the national range at $5,903 to $13,377, Bob Vila at $5,727 to $12,418 and Fixr at $7,500 to $14,000. Most of the spread is the material and the size of the roof.

You do not need to climb up to get a good number. The table uses a 1,700 sq ft footprint. Measure the footprint: the outside of the house plus the overhangs, as seen from above. Then multiply by the pitch multiplier. The multiplier is √(1 + (rise ÷ 12)²), which is just the length of the rafter for every foot it covers on the ground.

The calculator shows the full 1/12 to 12/12 table for your own footprint under the result. Divide the roof area by 100 to get squares, then add your waste allowance. Hips, valleys and dormers waste more shingles than a plain gable, so use what your own jobs have run.

The calculator gives the order list along with the price:

• Shingle bundles. Squares with waste times 3. Standard 3-tab and architectural shingles pack 3 bundles to the square. Some premium lines pack 4, so check the wrapper.
• Underlayment. A roll of #15 felt covers about 432 sq ft and a roll of #30 about 216 sq ft. Synthetic rolls cover more; use the maker's figure.
• Starter. Runs along the eaves and rakes. CertainTeed's SwiftStart covers 116 ft a bundle.
• Drip edge and ridge cap. Given in feet. Enter your measured edges and ridges, or the calculator estimates them from the footprint.

Worked example: a 1,700 sq ft footprint at 6/12 is 1,901 sq ft of roof. With 10% waste that is 20.9 squares, or 63 bundles of architectural shingles and 5 rolls of #15 felt.

• Material. The biggest lever. Tile and metal cost two to four times what asphalt does, and tile may need the framing checked for the weight.
• Size and pitch. More area means more squares. Steep pitches add area and slow the crew.
• Layers to tear off. A second layer doubles the tear-off work and the weight going to the dump.
• Complexity. Valleys, dormers, skylights and chimneys mean more flashing and more cutting.
• Decking. Rotten plywood found at tear-off is replaced by the sheet. Put a per-sheet price in your estimate so it is agreed before work starts.
• Where you are. Labor is a big part of a roof price. Bob Vila puts it at about 60%, Fixr at 40% to 60% and This Old House at 65%. The calculator scales that share by your state's construction wage.

Some costs only show up once the old roof is off. Build them into the estimate as unit prices so the customer agrees them in advance:

• Decking by the sheet, for rotten or delaminated plywood.
• Flashing around chimneys, walls and skylights, replaced rather than reused when it is rusted or bent.
• Ventilation: ridge vent, box vents or soffit vents brought up to the shingle maker's requirements. Most makers tie the warranty to proper attic ventilation.
• Ice and water shield along the eaves and in valleys where the code or the climate calls for it.

These come straight from the calculator at national prices: a 6/12 pitch, 10% waste and one layer torn off.

The same 1,700 sq ft footprint in each material, tear-off included:

The high ends sit above the national averages in the guides because they stack the high end of every part: the roofing, a heavy tear-off and the top of the labor range. Most jobs land near typical. Turn off the tear-off for a roof going over bare decking, such as new construction.

Worked example: architectural shingles on a 1,700 sq ft house.

Footprint 1,700 sq ft, 6/12 pitch, one layer off, national prices:

1. Roof area: 1,700 × 1.118 = 1,901 sq ft.
2. Roofing: 1,901 × $3.75 to $6.75 = $7,127 to $12,830.
3. Tear-off: 1,901 × $0.75 to $3.25 = $1,425 to $6,177.
4. Total: about $8,550 to $19,000, typical $13,775.

The same roof in a state with higher construction wages comes out higher, because the labor share is scaled. Put your ZIP in the calculator to see it.

A few missing shingles or one leak around a vent boot is a repair. These signs usually point to a full replacement:

• Granules in the gutters and bald patches on the shingles. The asphalt is wearing through.
• Curling or cupped shingles across whole slopes, not just one spot.
• Soft spots underfoot, which mean the decking under the shingles is wet or rotten.
• Daylight in the attic through the roof boards, or water stains on the rafters.
• Two layers already. Most codes allow no more than two layers, so a roof with two has to come down to the deck.
• Leaks in several places at once, after the flashing has been checked.

Show the owner photos of what you found. A roof replacement is a big number, and pictures of curled shingles and wet decking explain it better than words.

Most roofers price by the square and build the number from the parts: materials per square from the supplier's quote, labor per square, tear-off per square per layer, dumpster and permit, then overhead and margin. HomeAdvisor puts roofing labor at $200 to $300 a square before materials.

Keep a few separate lines on every estimate: the roof itself, tear-off, a steep or two-story charge if it applies, and a per-sheet price for decking. That way the customer sees what they are paying for and a surprise at tear-off is already agreed. Check your price with the profit margin calculator so overhead is covered before you send it.

"Save as an estimate in Koira" turns the calculator's lines into an estimate you can edit and send from your phone, with good, better and best options for the material.

A few habits keep roof jobs profitable:

• Measure, do not guess. Use the footprint and pitch for a first number, then confirm on the roof or from aerial measurements before you order. A wrong pitch on a big roof is several squares of shingles.
• Order from the take-off. The bundles, felt and starter from the calculator are a starting order list. Add hip and ridge, valley metal, pipe boots and nails from your own counts.
• Show options. Many owners pick the middle option when shown 3-tab, architectural and a premium line side by side. The calculator prices each one in seconds.
• Get the deposit. Materials are a large part of a roof. A signed estimate and a deposit before you order protect your cash.