Free Roof Replacement Cost Calculator (+ Guide)

What is a roof replacement cost calculator?

A roof replacement cost calculator adds up every cost of a new roof, from the roofer's quote to the gutters and permits around it.

It shows the total with a contingency, the cost per square foot and what's left of your budget.

How it works

The cheapest of your quotes goes in the total, next to the costs it doesn't cover.

What the building code says about reroofing

The 2024 International Residential Code sets the rules for replacing a roof or covering an old one.

• Replacement: a roof replacement removes the existing layers down to the roof deck (R908.3)
• Recover limits: no new layer over a roof that's water soaked or deteriorated, that's slate, clay, cement or asbestos-cement tile, or that already has two or more layers (R908.4)
• Flashing and vents: rusted, damaged or deteriorated flashings, edgings and vents are replaced (R908.5)
• Shingle slope: asphalt shingles go on slopes of 2 in 12 or steeper, with a double underlayment from 2 in 12 up to 4 in 12 (R905.2.2)

So ask each roofer whether the quote is a tear-off or a recover, and whether new flashing is in it. Your town may use another edition, so check with its building department.

How to compare contractors' quotes

The Federal Trade Commission gives this advice before you hire anyone.

• Hire only licensed and insured contractors, and check the license with your state or county
• Get several written estimates, each with the work, the materials, the completion date and the price
• Don't automatically pick the lowest bid, and ask why if the estimates differ a lot
• Get a written contract with the contractor's license number and the start and finish dates
• Never pay the full amount up front, and make the final payment only when the work is done

It also warns that a contractor who asks you to get the permits, or who only takes cash, may be running a scam.

How much contingency to add

A contingency is money set aside for what you find once the walls or the ground are open.

HUD requires one on its 203(k) renovation loans: 10% to 20% of the repair costs on a home 30 years or older, and at least 15% when the utilities don't work.

On a newer home, it's up to the lender, to a maximum of 20%.

A worked example

Here's the example the calculator loads: a 2,000 sq ft roof with three quotes of $14,500, $12,900 and $16,000, plus a sheathing repair allowance, new gutters and the permit.

The cheapest of the three quotes is $12,900, $3,100 less than the dearest. Your other costs add $3,300, so the roof replacement comes to $16,200 before the contingency.

A 10% contingency adds $1,620, for a total of $17,820. That's $8.91 per square foot, and $180 left of a $18,000 budget.

Mistakes to avoid

These are the slips that come up most.

• Comparing a tear-off quote with a recover quote as if they were the same job
• Leaving out sheathing repairs, which only show once the old roof is off
• Paying the full amount before the work is done, which the FTC warns against

Who is the roof replacement cost calculator for?

It's for anyone replacing a roof, after a storm or at the end of its life, and these tools help around it.

• Roofing calculator – for squares and bundles
• Square footage calculator – for the roof's area
• Home equity loan calculator – if you borrow for it

Know what each quote includes before you compare the totals, and the cheapest roof stays cheap.