In case you are thinking of replacing your roof, you will need some measurements of your roof. And to measure a roof, a standard procedure is determining the roofing square.

However,  you may not know about determining the roofing square. Hence, you might wonder about how to determine a roofing square.

A roofing square is basically a 100 square feet area of roof surface. Determining a roofing square is not that hard. You simply need to follow a specific procedure.

Let us discuss the whole process as elaborately as possible. In that way, you can determine the roofing square yourself.

How To Determine Roofing Squares

How To Determine Roofing Square 

You can easily measure a roofing square with the help of a few tools. You should start determining the roofing square after you have collected all the tools.

Necessary Tools

  • Measuring Tape
  • Ladder
  • Calculator 
  • Large Level
  • Pencil and Paper

Step by Step Procedure

Step 1: Ensuring Safety

The first step you should take is ensuring your safety. You should always get a good ladder. Additionally, wearing proper boots with enough traction is important. This will reduce the risk of your injury by a lot.

Step 2: Determining Roof Type

After you have ensured your safety, you should prepare yourself for carrying out the next step. You should be easily able to calculate the roofing square depending on the roof type. The roof may be flat or inclined. Hence, you should know what type of roof you have installed. 

Step 3: Finding the Area of the House

Now, you should collect the floor plan of your house. From the floor plan, find out the length and breadth of the house. However, you may not have the floor plan. In case you do not have a floor plan, take a measuring tape, then measure the length and breadth using the measuring tape.

You must include overhangs while measuring the length and breadth. You should measure twice or thrice to get an accurate result. However, note down the values in a paper. These values will be necessary later. 

Step 4: Calculation of Area of the House

In this step, you have to calculate the area of your house. The calculation of area depends on the shape of your house. If your house is rectangular, you can simply multiply the length and breadth of the house.

In case your house is trapezoidal, you should use the formula for finding out the area of a trapezoid. If you have a complex-shaped house, divide it into smaller shapes and find out the area.

Step 5: Finding Out the Pitch

After you have determined the area of the house, you should start by finding out the pitch. Firstly, you should take a large level. Then, with the help of a measuring tape, mark the line denoting 12-inch.

After that, you should prepare the ladder to climb the roof. Place it against the gable end of your house. Then, start climbing the roof using the ladder.

After you have reached the top, you should place the level. Put it adjacent to the gable trim as well as the flat touching the side of your house.

Then, You have to measure the level starting with the 12-inch mark to the lower part of the gable trim. You can find the rise of your roof from this measurement.

Generally, each rise is written as “ x in 12”. Here, the measurement of rising will replace the value x.  

Step 5: Calculation of Roofing square

This is the penultimate step for determining the roofing square. Firstly, you should divide the measurement of rising by 12. Then, you will need to find the square of the result.

The next step is adding 1 to the square value. Following that, determine the root of the new number. This is the pitch of your roof.

In case you have a flat roof, the area of your roof should be similar to the area of your house. However, in case your roof is a gable roof or cottage roof, you should do the following: 

You have to multiply the pitch by the area of your house. Adding 10% to the final number of the roof area,  you will get the total area of your gable roof. 

You should add 17% in case your roof is a cottage roof. This addition is due to allowance for hips, ridges and waste.

Step 6: Determination of Roofing Square 

This is arguably the easiest step considering the previous ones. You should divide the square footage of your roof by 100. With the completion of this calculation, you will have determined the roofing square.   

Sample Calculation

Let, the length of the house is= 50 metres.

The breadth of the house is= 40 metres.

The measurement of rise of the roof is 3 in 12.  

Now, area of the house= 5040 square metres

      =2000 square metres

Next, you have to do the following calculations: 

3/12 = 1/4

(1/4)2 =1/16

(1/16)+1 =1.0625

1.0625 =1.03

1.03 2000 = 2060

2060/1000 =2.06

The roofing square of this roof is 2.06.


We have tried to explain the process of determining the roofing square as easily as possible. We hope that you now understand the procedure of how to determine roofing square.

This is a tricky process. That’s why having some people to help you would be great. Once you have determined the roofing square, you can easily calculate the estimated cost of the roof replacement. 

If you follow the steps properly, you should not run into any problems. However, in case you face any difficulties, you can consult professionals. You can even hire some professionals to determine the roofing square for you. 


As a civil engineer and roofer, I love to share the experience that I have gained through the last couple of years. In the roofing industry, practical experience is a very crucial fact that can help you a lot. Hence, I want to help you with my blog.

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