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Roofing Calculator: How to Determine The Cost Of A New Roof

Roofing & Gutters
By on Mar 4, 2015
Roofing Calculator: How to Determine The Cost Of A New Roof

Your roof is one of the most valuable and expensive features of your home. It not only protects you from horrid weather, but also your home, foundation and landscaping. Therefore, before investing money in a new roof, it’s imperative to know exactly how to measure roof pitch, determine the right amount of squares (materials) and learn all the factors affecting the total cost.

ImproveNet’s roofing calculator and roofing cost estimators are the first steps in purchasing or building a new roof. Knowing the average costs of sealing, painting, repairing or installing a roof, as well as roof pitch and material estimates can go a long way in saving you hundreds, if not thousands, on your next roofing project.

Measure Roof Pitch

Roofing Costs

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According to our roof installation cost estimator, the average cost of a new roof is $5,951. There are many, many factors that can increase or decrease the overall price, such as materials, pitch and so on, but we have seen some roofing jobs exceed $12,000 and a few as low as $3,000.

Nonetheless, because there are so many options on the market, homeowners have the flexibility to make creative, thoughtful and timely choices. Knowing all your options below, as well as how to determine the number of squares with our roofing calculator, should inspire you to make the best decisions possible.

Roof Measuring

Before you begin your research, you must know how many squares you’ll need. In order to do that, you much first determine your roof’s slope, or pitch. Roof pitches are measured in terms of rise and run. The run is the distance from the outside edge of a perimeter stud wall to the center of the house. The rise is the distance from the top of a stud wall to the peak of the roof. A roof’s pitch is determined by how much it rises for every foot it runs. Thus, a moderate 6 in 12 roof pitch means the roof rises 6 inches for every 12 horizontal inches it runs. A 12 in 12 pitch is a steep, 45-degree angle roof.

While they are more costly, there are certain advantages of a steep roof:

  • Pitched roofs last longer.
  • Pitched roofs react better to inclement weather.
  • You can add an attic to a pitched roof.

Roof Pitch

How To Measure Your Roof Pitch

Before we move forward, note that some of these tasks are better left to the professionals. If you are thinking about fully replacing your roof, it’s always best to consult with a roofing pro. 

On the other hand, if you want to DIY, you can use one of these three methods to calculate your roof’s pitch. You’ll need a level and a tape measure. Mark a spot on the bottom of the level, 12 inches from one end. 

  1. On a ladder beside the roof, place the level a foot or so up the roof, hold it level, and measure from the 12-inch mark on the bottom straight down to the roof. If it measures 4 inches, you have a 4 in 12 pitch. 
  2. On a ladder at the gable end of your house, place the level against the rake rafter (the one on the roof overhang) with the 12-inch mark on the rafter’s bottom edge. Now, measure from the end of the level up to the bottom edge of the rafter. That is the roof’s rise.
  3. In the attic, place the level against a rafter with the 12-inch mark on the bottom of the rafter. Measure from the end of the level up to the bottom edge of the rafter. That is the roof’s rise.

Roof Types

Measuring Roof Area

Steep Roofs

Measure your house at ground level, then add in the roof's overhang for greater accuracy. As an example, if the roof overhang is 12 inches, you'll add two feet to the overall length and two feet to the overall width of the house. This nominal square footage amount is then multiplied by a factor associated with the roof's pitch. See the table below for exact measurements. Keep this number handy.

Pitch     Multiply by:
4 in 12 1.06
5 in 12 1.08
6 in 12 1.12
7 in 12 1.16
8 in 12 1.20
9 in 12 1.25
10 in 12 1.30
11 in 12 1.36
12 in 12 1.42

Flat Roofs

While they may not be as aesthetically pleasing, flat roofs are certainly easy to measure. If your roof is flat or less than than a 3 in 12 pitch, all you have to do is multiply the width by the length.

Roofing Calculator

You are ready to determine how many squares you need for your roof. Click on the image below to head to our roofing calculator and determine how many squares you need to replace your entire roof.

Roofing Calculator Example

Cost of Roofing Materials

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Now that you know the size of your roof, or how many squares you need, you can determine the cost of materials. As you can imagine, this knowledge can become a great bargaining chip when discussing bids.

Most roofing contractors give their materials cost in terms of 10 ft. x 10 ft. squares (100 square feet). This is why your number of squares was so low on your roofing calculation. Most materials cost about $150 per square, but for specific materials, please see below.

  • Membrane (Modified Bitumen): $50 per square
  • Asphalt Shingles: $125 per square
  • Slate: $130 per square
  • Wood Shakes or Shingles: $180 per square
  • Clay Tiles: $210 per square
  • Metal: $500 per square
  • Copper: $1,100 per square 

Other Cost Considerations 

Like any remodeling projects, there are always other factors affecting the overall price of the project.

As I already stated, the steeper a roof, the more costly it is to replace (or build). Not only do they require more materials, but they take longer to install and are more dangerous. Working on a curve is lot more difficult than working on a flat surface. In fact, many contractors adjust their pricing after a minimum pitch to account for the added dangers of working on a steep slope.

Complex roofs, just like complex flooring or wall murals, will cost more than your standard roof. Therefore, chimneys and skylights will raise the budget. While the following features should not be considered complex, given their importance as they relate to water damage, they do increase the total cost.

  • Gutters
  • Drains
  • Extra vents
  • Flashing

Finally, removing an existing roof, working on top of a damaged roof or modifying an existing roof’s structure can all increase the total cost of your project. 

Roof Installation

DIY vs. Hiring A Pro

Installing or repairing your own roof can be very dangerous. The roof is a very valuable asset when it comes to your home and should be treated as such. While you would save money by doing it yourself, most of the time, homeowners opt for a pro.

The cost of labor for roofing is generally equivalent to the cost of materials for that roof. If you chose to DIY, you could save about half the money you would otherwise spend. Just know, a contractor can most likely finish the job in half the time.


Roofing is key to a property's value, so it's vital to spend enough to sustain this very important investment. Now that you know how to measure roof pitch, determine squares needed, as well as the average costs for the most popular roofing materials, you can make educated decisions to determine how much you should spend on a new roof.

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