Roof replacement cost calculator

How to estimate a roof replacement in five steps

1. Measure the house. Enter the length and width of the house footprint, the overhang and the pitch. The calculator turns them into roof square feet and roofing squares.
2. Pick shingles and extras. Choose the shingle type, how many old layers come off, and any decking, vents or chimney flashings you know about.
3. Type your prices. The quantities show at once. Where we have no sourced number the price box is empty: type your own, and each line, the total and the range fill in with the source and date of every number.
4. Compare bids. Enter two to four bids and the squares each covers. See each per roofing square, and tick what each one says it includes.
5. Print the sheet. Download a one-page sheet in English, Spanish or both to bring to every contractor you talk to.

What this calculator does, and what it does not

A roof estimate here is a range, not a single number. Once every line has a price, each line shows a low and a high, and a typical price where real data stands behind it. Each number carries a source and a date, so you can see where it came from and how old it is. The quantities, squares and bundles, always show, because they are geometry.

It is an estimate, not a quote. A quote comes from a roofer who has stood on your roof. No calculator can see rotten decking, old flashing or storm damage, which is why the page says inspection needed. We never ask for a phone number, an email or an address, and nothing you type is sent anywhere.

How the roof's size is worked out

Roofers price in squares. One square is 100 square feet of roof. To get there, the calculator adds the overhang to every side of the house footprint, multiplies the length by the width, and then multiplies by a pitch factor, because a sloped roof is bigger than the floor under it.

The pitch factor is the square root of 1 plus the rise over 12, squared. A 6 in 12 roof has a factor of about 1.118. Take a house 50 feet long and 30 feet wide with a 1 foot overhang. The footprint with the overhang is 52 by 32, which is 1,664 square feet. Times 1.118, the roof is about 1,860 square feet, or 18.6 squares.

Waste, bundles and why you order more than the roof's size

Shingles are cut at the edges, hips and valleys, and some are lost to mistakes, so a roofer orders more than the roof's area. The calculator adds 10 percent for a simple roof, 12 for a moderate one and 15 for a complex one. Those are common rules of thumb, and you can change them.

Most shingles come three bundles to a square. With 10 percent waste, the 18.6 squares above become 20.5 squares, which is 62 bundles. The calculator rounds bundles up, because nobody can buy part of a bundle.

Shingle types: 3-tab, architectural and premium

Three-tab shingles are the thinnest and the cheapest. Architectural shingles, also called dimensional, are thicker, layered and the most common choice for a house today. Premium shingles are heavier and cost more again. Prices differ by brand and by supplier, so the starting prices are ranges, and the page asks you to type your own when you have a supplier quote.

Tear-off, layers and disposal

A new roof usually goes on a bare deck, which means the old shingles come off and go to a dump. Each layer of old roofing adds labor and disposal. Many places allow a second layer to be left on, and many roofers advise against it. Ask each contractor what they plan to do and write it down.

Where the numbers come from

The labor wage is public data: the Bureau of Labor Statistics survey of what roofers in the San Antonio area earn, with the 10th percentile, the median and the 90th percentile. It is straight-time pay, so the calculator multiplies it by a labor burden taken from the Bureau's compensation cost series, which covers payroll taxes, insurance and benefits.

The prices of materials, disposal and extras are left empty until real job costs are available, because we do not invent numbers. Each empty box says Type your price. When you type a price, that line is priced with it, marked as typed by you, and the total appears once every line has a price. We do not copy prices from other calculators or price guides.

How to read a roofing quote

Compare quotes on the same scope. A bid that leaves out tear-off, decking, vents or the permit can look cheap and cost more in the end. The bid check lists the items worth confirming with each contractor, and shows each bid per roofing square, so a 20-square job at $9,000 and a 19-square job at $9,500 can be compared fairly: $450 and $500 per square.

• Is the old roof torn off, and is the disposal included?
• What underlayment goes down, and are drip edge and flashing included?
• What happens if rotten decking is found, and what is the price per sheet?
• Is the permit included, and who pulls it?
• What is the workmanship warranty, and is it in writing?
• How long will the job take, and what is the cleanup plan?

What an estimate cannot see

A calculator works from numbers you type. It cannot tell if the deck is soft, if the flashing around a chimney has failed, or if hail has damaged the roof. Those are found on the roof. That is why every result says inspection needed, and why a quote from a roofer who has inspected your roof is the number that counts.

Texas and San Antonio notes

For questions about insurance, claims or roofing contractors in Texas, the Texas Department of Insurance is the place to start. For re-roof permits in San Antonio, the city's Development Services Department has the application and the current fee. Both are linked in the tool. This page gives no advice on insurance, permits or contracts.

Your answers and your privacy

The calculator runs in your browser. It has no place to type a phone number, an email or an address, nothing you enter is sent to a server, and nothing is saved when you close the page. Print the sheet if you want to keep the numbers.

Frequently asked questions