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Roofing Calculator

Roofing Calculator

Provide your roof measurements to this free roofing calculator and calculate the roof area and its construction cost.

House Length:


House Width:


Roof Pitch:


Unit Price:




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The roofing calculator allows you to calculate the area of the roof and find out how much you will have to pay to reconstruct it.  

With this online tool, you can get a free roof estimate in no time 

Roof Area Formula:

Use the following roof equation for a roofing estimate:

Roof area = base area / cos[pitch(deg)]

How To Calculate Roof Size And Its Cost?

If you are going to construct a roof, then you will need to have the correct size of the roof so that you can have a precise roofing estimate.

Roofs are measured in square footage and the contractors take the project on the basis of roof size and provide the roofing quote. 

In this regard, an online roof calculator is very useful. As it allows the contractors to get free roofing estimates.

Follow the below-mentioned steps to calculate the roof area and cost:

Measure the Roof Size:

  • Determine the length and width of the roof
  • Calculate the base area by multiplying the length with the width
  • Find the roof pitch with the help of the following formulas

pitch(%) = x / 12 × 100%

pitch(deg) = arctan[pitch(%)]

  • Now get the roof area with the help of the pitch
  • Put the value of pitch in the formula of the roof area


  • Calculate the area of the roof
  • Now get the unit price for roofing
  • Multiply the roof area by the unit price and that’s it

This estimation helps in buying the correct amount of Asphalt shingles for constructing the roof.

If you want to save time, then simply use a roof shingle calculator and get a roof estimate online from your browser without installing any additional program. 

Practical Example:

Let’s suppose you have a house with the following roof Dimensions

  • Length (L) = 40 feet
  • Width (W) = 30 feet
  • Pitch = 5%

Now estimate the roof size and cost.


Area = Length x Width = 40 x 30 = 1200

Pitch Deg = arctan[pitch(%)] 

Pitch Deg = arctan[5%] = arctan[0.05]

Pitch Deg = 2.86 degree 

Now put the value in the roof area formula:

Roof Area = base area / cos[pitch(deg)]

Roof Area = 1200 / cos (2.86)

Roof Area = 1200 / 0.9988 = 1201. 5 ft^2

Roof Area = 1201. 5 ft^2

Unit Price = 5 

Cost = 1201.5 x 5 = 6007.5

If you don’t understand this calculation, then use a roof calculator. With it, you will be able to get the online roofing estimate (roof size and cost) in no time. 

Roof Pitch Table:

Find the roof area by using multipliers for the specific roof pitch that we have provided in the following table. 

Pitch Angle Multiplier
1/12 4.8° 1.003
2/12 9.5° 1.014
3/12 14.0° 1.031
4/12 18.4° 1.054
5/12 22.6° 1.083
6/12 26.6° 1.118
7/12 30.3° 1.158
8/12 33.7° 1.202
9/12 36.9° 1.25
10/12 39.8° 1.302
11/12 42.5° 1.357
12/12 45.0° 1.414
13/12 47.3° 1.474
14/12 49.4° 1.537
15/12 51.3° 1.601
16/12 53.1° 1.667
17/12 54.8° 1.734
18/12 56.3° 1.803
19/12 57.7° 1.873
20/12 59.0° 1.944
21/12 60.3° 2.016
22/12 61.4° 2.088
23/12 62.4° 2.162
24/12 63.4° 2.236

How Does Our Roofing Calculator Work?

Calculate the roof size to determine the number of shingles you need for your project and the cost of the roof by just providing a few simple inputs to this roofing estimator. Let’s see how it works!

What Do You Need to Enter?

  • Roof Dimensions: Add the correct length and width of your house 
  • Roof Pitch: Provide the measurement of the vertical rise of the roof by its horizontal run
  • Unit Price: Add the price per square

This is What You Will Get!

  • Roof Area in various units
  • Total Cost
  • House Base Area
  • Roof Pitch
  • Roof Pitch (x:12)

This roofing cost calculator is designed to calculate the size of the roof, as well as the amount required to build the roof of a specific dimension.

However, it’s a very useful tool for contractors as it allows them to provide the roof quote. Through it, they can get free roof estimates instantly!


What Is The Most Common Roof Pitch?

The standard roof pitch lies between 10 – 25 degrees. If your house is located in a hilly area where snowfall happens too much, then it’s good to choose a higher (steeper roof). 

How Many Shingles Do I Need For a 1200 Square Foot House?

You will need to have one or two shingles per square foot according to the type and size of the shingle that you want to apply. To get a precise estimation in seconds,  use a roofing calculator.

What Are Gable And Shed Roofs?

A Gable roof means to have a roof that has two slope sides meeting at a ridge and on the other hand, a shed roof means to have a roof that contains only one flat surface which slopes to one side. 

References: How to Estimate & Price a Roofing Job.