Roof Repair or Replace Calculator

The calculator compares cost per year

The tool compares two numbers, both per year. A repair costs its price divided by the number of years it keeps the roof going. A new roof costs its price divided by its whole expected life. Whichever is lower is cheaper to own, at least on paper.

Remaining life = expected life − roof age (never below zero).
Repair per year = repair quote ÷ years the repair buys. Default is the remaining life, with a floor of one year. Change it if your roofer says otherwise.
Replacement per year = replacement cost ÷ expected life of the new roof (same material).
No quote yet? Replacement = squares × (installed price + one layer of tear-off), and the math uses the middle of that range.

Here is the default roof worked through: architectural shingles, 18 years old, a $1,200 repair, 25 squares and no replacement quote. Expected life is 30, so 12 years are left. Replacement comes to 25 × ($450 + $100) = $13,750 on the low end and 25 × ($750 + $150) = $22,500 on the high end, with a middle of $18,125. That's $18,125 ÷ 30 = about $604 a year for a new roof.

The repair is $1,200 ÷ 12 = $100 a year, and it's only 7% of a new roof's price. The roof has used 60% of its life, 10% of it is damaged, and it has had one leak. No warning signs trip, so the answer is repair.

Age that same roof to 26 and give it three leaks in two years, and the answer changes. Life used jumps to 87% and the leak count trips too. With two signs tripped, the tool says replace, even though the per-year math still says the patch is cheaper. That gap is intentional. A repair on a tired roof rarely buys the full remaining life. It buys time until the next spot goes.

How long does each roof material last?

About 20 years for 3-tab shingles, 30 for architectural, 40 to 80 for metal, 60 to 150 for slate and 25 for wood, per the InterNACHI life expectancy chart. The calculator's expected lives come from that chart. Where the chart lumps materials together, the numbers match the site's guide on how long a roof lasts.

Screw-down metal gets 25 years, because the rubber washers give out long before the steel. Standing seam gets 50. Concrete tile gets 40 and clay 75, because the underlayment under tile fails well before the tile does.

Material	Typical life	Used in math	Installed, per square
3-tab asphalt shingles	15 to 20 yrs	20 yrs	$380 to $550
Architectural asphalt shingles	22 to 30 yrs	30 yrs	$450 to $750
Metal, exposed fastener (screw-down)	20 to 30 yrs	25 yrs	$600 to $1,000
Metal, standing seam	40 to 80 yrs	50 yrs	$1,000 to $1,600
Wood shakes or shingles	20 to 30 yrs	25 yrs	$900 to $1,400
Concrete tile	30 to 50 yrs	40 yrs	$900 to $1,600
Clay tile	50 to 100 yrs	75 yrs	$1,500 to $2,500
Natural slate	60 to 150 yrs	100 yrs	$2,000 to $4,000
Flat roof (EPDM, TPO, mod bit)	15 to 25 yrs	20 yrs	$550 to $1,100

Knock some years off for a hot climate, a stuffy attic or a cheap install. For a replacement price on your exact roof size and material, the roof cost calculator gives you squares and a range you can paste into the quote box above.

Two warning signs mean replace

When two or more signs trip, the tool says replace. When one trips, it says get an inspection, because one sign alone can go either way. The tool uses four rules of thumb that roofers rely on, plus the per-year check:

Repair over about 25 to 30% of a new roof. You're putting real money into something with a short future.
Past about 75% of expected life. Shingles that old crack when you lift them to work the repair in.
A quarter or more of the roof damaged. Patches that big don't match, and the old underlayment under them is still old. The repair vs. replacement guide calls this the 30 percent rule.
Two or more leaks in two or three years. Leaks in different spots each time mean the whole surface is failing. More on that in signs you need a new roof.

Florida has a strict version of the damage rule. The Building Code's 25% rule used to force a full reroof when more than a quarter of a roof was repaired within a year. In 2022 the legislature exempted roofs built under the 2007 Florida Building Code or later, so on those only the repaired part has to meet current code (Florida Statutes 553.844).

The 2007 code didn't take effect until March 1, 2009, and the Florida Roofing and Sheet Metal Contractors Association says checking permit records is the only sure way to know which code a roof was installed under. Older roofs can still trigger a full replacement.

The calculator can't see hidden damage

Rotted decking, wet insulation and a bathroom fan venting into the attic can all change the answer, and none of them shows up in a quote. The repair price itself is a guess until someone pulls shingles back. A small leak around a pipe boot usually runs $300 to $800, and flashing work costs more. The ranges are in roof leak repair cost.

A storm claim can beat the per-year math

If a storm did the damage, an approved claim can turn a $15,000 replacement into a deductible, and that beats any per-year math. Get the inspection first, file the claim second, and sign a repair contract last. Getting insurance to pay for a roof walks through the claim.

Roof repair or replace questions

When is it better to replace a roof than repair it?

When two or more of these signs line up: the roof is past about three quarters of its expected life, the repair costs more than a quarter of a new roof, a quarter or more of the surface is damaged, or leaks keep showing up in new spots. One sign alone is a judgment call. Soft decking means replace on its own.

What is the 25 percent roof rule?

It's a Florida Building Code rule that used to force a full reroof when more than 25% of a roof was repaired or replaced within 12 months. Since 2022, roofs built to the 2007 Florida code or later only need the repaired part brought up to current code, but older roofs can still trigger it. Other states have no such rule, though some insurers and towns have their own.

How many years does a roof repair add?

On a young roof, a good repair can carry it to the end of its normal life, sometimes 15 or 20 years. On an old roof it fixes that spot and nothing else, so a couple of years is a more honest estimate. The calculator starts with the roof's remaining life and lets you change it.

Will insurance pay for a new roof?

Sometimes, if a covered storm caused the damage and the roof wasn't simply worn out. Policies that pay actual cash value subtract depreciation first, so an old roof gets a small check. Get an inspection and read the policy before you sign a repair contract.

How do I know how much life my roof has left?

Start with the material's typical life (about 20 years for 3-tab and 30 for architectural shingles, per InterNACHI) and subtract the roof's age. Then adjust for what you see. Curling, bald spots and brittle tabs mean less time than the math says.