Roof replacement cost calculator

How to estimate roof replacement cost

Roof replacement cost is the number of roofing squares times the installed price per square in your bid, plus extra tear-off, permits and flashing. A square is 100 sq ft of roof surface, the unit roofers price and shingles are sold by. The work is in finding the squares, because the roof is bigger than the footprint of the house:

Roof area = plan area × √(1 + (rise ÷ 12)²)(50 + 2) × (30 + 2) = 1,664 sq ft of plan × 1.1180 = 1,860 sq ft

The plan area includes the overhang on every side. The same multiplier works for a gable or a hip roof as long as every plane has the same pitch, because each plane is tilted by the same angle. Dormers, valleys and porches with a different pitch need to be measured separately and added; enter the total in Known roof area. The square footage calculator handles footprints made of several rectangles.

What roofing jobs cost in the national survey

Roofing is the costliest common home improvement in the Census Bureau's American Housing Survey: 8.3 million roofing jobs by homeowners in the two years to 2023 had a median cost of $10,000 and an average of $11,610, about $93.5 billion in all.^[1] These are national figures for every kind of roofing job, large and small, and they include work owners did themselves; across all projects, about 36% were do-it-yourself.^[2] They tell you what is typical, not what your roof should cost.

The builders' figure from NAHB is for new construction, with no old roof to remove.^[3] A replacement adds tear-off, disposal and any deck repair, which is why the calculator asks for your bid's price per square rather than using a national number.

Tear-off, layers and the deck

A roof replacement removes every existing layer down to the deck; the model residential code treats a covering laid over an old one as a separate case, a roof recover, with its own limits.^[5] Most bids price one tear-off into the per-square price. If your roof already has a second layer, enter 2 in Layers to tear off and the per-square price your roofer quotes for the extra layer.

Worked example

1. Footprint with overhangs: (50 + 2) × (30 + 2) = 1,664 sq ft.
2. 6/12 pitch factor: √(1 + 0.5²) = 1.1180, so the roof surface is 1,860 sq ft.
3. With 10% waste: 1,860 × 1.10 ÷ 100 = 20.5 squares, or 62 bundles at three bundles a square.
4. Cost: 20.5 × your installed price per square, plus any extra layer and other items. Two bids priced per square can be compared directly.

Shingle packaging varies: three bundles per square is common, but some heavy laminated shingles come four to a square, so check the wrapper before ordering.

Comparing roofing bids

• Price per square and the number of squares. If two roofers measure very different squares, ask how they measured.
• Layers removed and disposal. Confirm the bid includes the layers your roof actually has.
• Deck repair. Ask for a price per sheet of replaced sheathing, since rot shows only after tear-off.
• Flashing, vents and underlayment. These are where bids differ most when the shingle line is the same.
• Permit and warranty terms. Get both in writing.

The builders' life-expectancy study rates asphalt shingle roofs at about 20 years, a general guideline that depends on quality and upkeep.^[4] For other materials, see the metal roof cost calculator; new gutters often go up with a new roof, and the gutter installation cost calculator sizes them.

Paying for a new roof

A roof is often paid from savings, a home equity loan or a HELOC. Interest on home equity debt is deductible only when the money is used to buy, build or substantially improve the home that secures it, and the IRS counts improvements that prolong the home's useful life.^[6] The CFPB also warns to beware of contractors who show up uninvited offering a loan to pay for repairs.^[7] Compare monthly payments for your bid total in the home improvement loan calculator, check how much you could borrow with the HELOC LTV calculator, or see the payment on a line with the HELOC payment calculator.