How To Use Our Free Roofing Calculator

In this guide, we will walk you through the easy steps to get the most accurate price estimate with our free online roofing calculator. We will also cover some of the specifics of how we calculate roof prices, and why our results may be different from those that you may get from contractors who estimate your roof in person. You can read this guide first, or proceed to calculate roofing prices now.

Please note – some of this information here moved from the home page to make navigation easier and less cluttered.

How To Estimate Roof Prices Using Our Calculator

To calculate a roof you need to first understand which roof type you are dealing with. The most common is a gable roof, followed by a hip roof. Very often a roof is a combination of styles, with the addition of valleys, dormers, etc. See the diagram below for a detailed explanation of what is what on the roof.

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Once you’ve determined the type of your roof structure and additional components / penetrations and flashing details, you will able to select appropriate roof difficulty, and other details (custom field).

image of roof construction diagram

Roof Calculator Custom Fields

Roof size

You will also need to get the roof’s ground dimensions to insert roof sizes. Just take a measuring tape and get rough ground dimensions of your house. Do not forget to include roof overhangs, as they may add a significant amount to the total area.

Roof Difficulty

You need to identify you roof style, additional components, such as skylights, chimneys, dormers and determine the roof’s difficulty level. For example, the roof in a diagram above, is about medium level of difficulty. The reason is that this particular roof is a non walker – the roof’s pitch is about 10 in 12. It has a dormer, hips, sidewall and different levels on the same plane (see how the eave on the left hand side is much lower than the right eave).

Roof Pitch/Slope

To determine whether you roof is walkable or not you can use two methods. One – actually get up there and try to walk. Just kidding of course – walking on the roof is quite dangerous! We recommend using a simple protractor. You can also use a level, together with measuring tape.

Basically roof pitch is determined by a it’s rise to a it’s run ratio. To measure the run For run you take 12 units (usually inches) and measure the rise. A 12 in 12 pitch (or simply 12 pitch) is a 45 degree angle.

Check out our comprehensive guide for more information on measuring and calculating roof pitch using level + tape measure or simple geometry and the Pythagorean theorem.

Roof tear-off / removal – select how many layers of old roof covering needs to be removed.

On most re-roofing jobs, old covering materials should be removed to allow access to the substrate (in case any carpentry work needs to be done) and to install new underlayment. It is also a good practice to remove old materials to improve ventilation of the roof deck. Also, most manufacturers will void material warranty, if the old roof was not removed.

Number of floors / stories in your house

Essentially – the taller your house is, the more you are going to pay, as it becomes increasingly more difficult for roofers to work on taller homes. Additionally – roofs are usually steeper on 2-3 story homes, compared to a typical ranch (1 story) house.

Chimneys and skylights

Chimneys are necessary to vent your heating systems, and skylights are nice to have to brighten up your home, and improve cooling. However these protrusions make installation process more difficult and slow, so most contractors will charge an additional amount for each skylight or chimney flashing.

Ridge Vent

Ventilation is essential for any roof to last for a long time, and ridge / soffit ventilation system is one of the most effective “passive” ventilation types in residential construction. However, it will not work for every house. For example – if your home has a “gable” type roof, ridge vent will not work for you, as there is no way for air to circulate through the rafters. Also, ridge vent is not very effective for hip roofs. And finally, there should be space between the rafters for air to circulate. If all these criteria are met, choose the length of your ridge to get pricing for a new ridge vent.

Plugging Information Into the Calculator

Once you determine the pitch of the roof, plug in your numbers and other information into the calculator and click the “Calculate” button. The results will appear right below. Do not forget to include skylights / chimneys, as these add significant installation time and will increase your actual roofing costs.

When measuring your roof and using our calculator, be honest with yourself. If your roof is difficult, do not use the medium setting, as you will get the wrong results and will be disappointed to get a higher than expected price quote from your local contractors. To get more accurate results, read our extensive roof estimating and measuring guide.

Limitations of Our Calculator

This tool was designed to cover nearly all major types of roofing materials at the same time. Therefore, the prices, which it provides may be a “little off”. This is in part due to different realities of the generic roofing market (asphalt shingles installation) vs. specialty roofing markets such as metal roofing, slate / tile roofs and flat roofing. Thus, there will be a discrepancy with real world prices that you can get from your local contractors.

We had to adjust the results to fit both ends of the roofing market’s spectrum, where the same procedures may and will be charged for differently, depending on which type of roof you are purchasing. A good example would be the cost of chimney or sky-light flashing. In case of asphalt shingles roof installation, the contractor will 95% of the time reuse the existing lead flashing. At the same time, a metal roofing system WILL require the removal of old lead step-flashing and installation of custom-made single piece counter-flashing. Same is the case with skylights; where there is a generic skylight flashing which comes with the unit, and is designed for asphalt shingles roof, but is unusable for metal roofs or tile.

Another major limitation, which is related to the one listed above, is the fact that tear-off costs will have a significant difference in price between asphalt shingles installers and specialty roofing contractors dealing with metal roofing, slate, tile, etc. Also, when it comes to flat roofing, the contractor’s actual cost of tear-off and disposal is significantly higher than that of a shingle roof. For example, we will take one layer of asphalt shingles weighing 250 lb. per square and tar and gravel roof weighing about 800 lb. per square. The removal process of a tar and gravel flat roof is also much more complicated, tedious, and overall more difficult, and as a result will cost more.

Because of these multiple complicating factors, as well as those described below, we made our roofing calculator to be more generic and all inclusive. We will introduce a specialty calculator for Metal Roofs and Flat Roofs in the near future. These calculators will be more accurate, and will also include more material choices.

Real World Roofing Price Variations

We want you to understand that the roofing prices provided by this calculator are approximate and will vary from region to region, depending on the local economic situation, cost of living and real estate prices, as well as other factors. Prices are provided assuming you hire a fully licensed and insured, reputable roofing contractor.

As an example of price variations, a price of a 30-year dimensional (architectural) shingles roof for a 1 layer tear-off on a 1 story walkable gable roof (a simple ranch house) in Boston is about $375-425 per square (100 sq. ft.). The same roof somewhere in Indiana may cost $250-275 per square. Therefore, after much research on national price levels we put together approximate average prices for asphalt shingles, metal roofing systems and flat roofing membranes.

Also, we had to average the cost of roof tear-off and disposal. Do understand that while somewhere in Alabama it costs about $20 to dump 1 ton (2000 pounds) of old roofing materials, in Massachusetts and Connecticut, the disposal fees are $90 per ton. Therefore, you are looking to pay about $30-50 more per square of tear-off in New England. Here, is a good informational thread on about roofing price/square in different regions of US.

As for metal roof installation, the prices we have provided are more or less in line with national prices, but also keep in mind the local factor. Another thing you really need to account for is the level of experience of a metal roofing contractor giving you an estimate. Often, you will get a seemingly low price for a metal roof, but be aware that it may be coming from a desperate contractor in need of work. Chances are that this contractor is uninsured.

Another possibility is that you are dealing with a roofer who is new to metal roofing and A) does not know the price levels suitable to run a metal roofing company, and B) is inexperienced in installation of various metal roofing systems. In the second case, as our experience shows, these roofs begin to leak very soon after the installation. The truth of the matter is that any roofer cannot just install a metal roof. There is a great deal of special training involved in the installation of trim, flashing around chimneys, skylights and along valleys. Roofing underlayment must also be installed differently from shingle roofing felt. Therefore, an untrained roofer will 95% of the time screw up the installation, resulting in leaks. After speaking with my suppliers, I have learned that most first-time metal roofers never buy the product again and there are also usually warranty issues between the customers and suppliers / manufacturers, due to faulty installation.

Our Calculator Estimates Prices For the Following Materials

Sloped Roofs – Asphalt Shingles, Interlocking Steel and Aluminum Shingles, Standing Seam Metal Roofing.

Flat Roofs – IB membrane (PVC), EPDM Rubber and Modified Bitumen (torch-down), as well as newer TPO roofs.

Energy-Efficient Cool Roofs: Along with roof prices, the calculator will also estimate your approximate annual energy savings achieved when you install a Cool Roof. This can either be a Metal Roof or a Flat roof such as PVC and TPO (which are usually white and cool roofs, similar to PVC membranes).

Learn more about roofing materials featured in our calculator – product details, pros and cons of each roof type and approximate installation price per square.

Additional Resources For Accurate Roof Measurement and Estimation

Roof measuring guide – learn ho to accurately measure your roof, to get proper dimensions, roof pitch, and other specifics, that will determine how big your roof is, and the cost of replacement.

Roof estimating guide – learn how contractors arrive at their roof replacement costs. Once you can accurately measure your roof, with this guide you will be able to estimate your replacement cost and determine if your roofer is charging you TOO much or not.

Roofing square guide – roofing square is an area measuring unit used by US and Canadian roofers and other contractors, and equals to 100 sq. ft. or a 10×10′ section of a roof. See why North American roofers use “squares” and how they incorporate them into their price structure.

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5 thoughts on “How To Use Our Free Roofing Calculator

  1. Kyle Parnell

    I don’t see how GPS gets involved with your
    app. I bought the app for my iPhone. Does it operate on my current address’s roof where my iPhone is located to calculate the roof dimensions? I thought the GPS was used to keep from having to measure a roof?

    1. Leo - roofer with a vision Post author

      Hi Kyle,

      GPS gets the address of the roof you are estimating, to save you time. It does not measure the roof for you – you need to measure the ground dimensions and plug them in on the main screen.

      Back to GPS – it pulls your address based on your coordinates. You can later change that address – say you measured the roof and then used the app few houses down the street – you can adjust the address.


  2. Trevor Bowering Post author


    Thanks for the response. Ball park cost for customization as I am sure you have done the same thing for other roofers. Also, I just downloaded your App today on my ipad and have to set it up with my own pricing and give it a try.

    On another note, what is your guys main business? Are you a roofing company? What is in it for you to provide a free roofing calculator for people to download onto their website? I know you now sell the App but what about the free version, what is the story there? Just curious


    Trevor Bowering, Owner

  3. Trevor Bowering


    I own a roofing company in Ontario Canada and note that one of your other customers had asked about customizing this tool specifically for the Ontario market. Was that ever done or can it be done? More specifically if I gave you my numbers would you be able to customize this tool so that I can down load it onto my web site?


    Trevor Bowering