How To Calculate Square Footage

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When you are looking for a place to live it is very common to ask about its square footage. This refers to the place’s area measured in units of square feet. Everywhere in the world with the exception of just a few countries, this would be measured in square meters. But no worries! It is pretty easy to convert one into the other. Keep reading to learn how.

Usually, the bigger a house is, the more expensive it will be in a given area of a city. On the other hand, if you want to sell your house it is essential that you report its square footage to potential buyers, so they can compare it to other options in the market. 

This is why learning how to calculate the square footage of any space, whether you plan to sell it, rent it or even renovate it, is a very useful skill to have. Let’s discover how to do it for commonly- and irregularly-shaped rooms. 

How to calculate square footage

To calculate a flat space’s square footage follow these steps: 

  1. Divide the entire area into as many adjacent common shapes (rectangles, triangles, circles, etc.) as you need without leaving any uncovered space.
  2. Calculate the area of every shape independently in square feet, using the following equations. To do so, make sure the lengths and radii are in feet. 
Shape Area
  1. Add all of the resulting areas together to calculate the room’s total square footage:

What is square footage

An area is the amount of two-dimensional space covered by any surface. You can also think of it as the space enclosed by any flat closed curve, meaning one which starts and ends at the same place. 

Think about a rope. If you tie both its ends together and lay it on the floor you can produce an infinite amount of shapes. The following image shows three possible configurations. The rope represents the perimeter of the shape, and the space enclosed by it is its area. The former is fixed in this case, because the rope does not change its total length. On the other hand, the total area depends on the shape that you create with it. 

Different flat shapes have different areas, or cover different amounts of space, as long as the perimeter stays the same. If the perimeter of a shape increases, it will be able to enclose a bigger space, meaning its area will increase, while if it decreases, the total area enclosed by it will be less. 

How an area is measured depends on the specific shape enclosing it. Since it is essentially flat, it spreads over bidimensional space, which implies it has a width and a length. In principle, the area is determined by multiplying these dimensions. Since both are measured in meters, the area has units of square meters. 

In the United States, Canada and the United Kingdom, feet (ft) are widely used as a unit for length. In the rest of the world meters are used instead. The relation between one and the other is the following: 

This means that an area can be measured both in square meters and square feet. To convert one into the other fractions can be used. Since 1 m equals 3.3 ft, then their ratio must be equal to 1, and since multiplying any number by 1 yields the same number, we can write the following equation:

So, in order to convert square meters to square feet, you just need to multiply the former by 10.8. 

In these examples we have been dealing with flat shapes. But what happens when a shape is not flat but bumpy and uneven? What is its area then? This happens, for example, with land terrains which have hills or slopes.

Imagine you have a piece of cloth big enough to cover the entire uneven terrain. Since fabric is flexible it will be able to take the three-dimensional shape of the land. Once entirely covered, you cut the cloth following the terrain’s boundaries, so that its entire area matches that of the land. 

If you then extend the fabric on a flat surface you will be able to measure a flat area as big as the surface of your terrain. In this scenario, the area is called surface area. Although it might sound redundant, using the word “surface” just implies that the area being measured is distributed on top of a 3-dimensional object.

Now, most homes have flat floors, even if distributed in different spaces with different heights. This makes measuring the total area of a room or an entire apartment or house, a lot easier. 

Since square feet is the most common unit to measure areas in countries which use the imperial system, the square footage of any space simply refers to its area measured in said units.

How to measure the square footage of a rectangular room

Most rooms or living spaces are rectangular. This means their square footage matches that of a rectangle with the same width and length as the room. In this case, its area is calculated by multiplying both dimensions. Look at the following image. The width of the room is 12 feet, and its length is 16 feet.

The total square footage of the room is then: 

Remember there is no real difference between the width and the length of a rectangle. We only use these words to differentiate both dimensions from our perspective. 

How to calculate the square footage of an irregular room

Sometimes, architects get a little more creative than usual and design spaces that no longer have simple rectangular shapes. How can we measure the square footage of such a space then?

In this case, a very useful option is to fit common shapes, which areas are known, into the space you want to measure. Take a look at the following image. Although the room is not a simple rectangle, it can be thought of as the sum of two adjacent rectangles:

The area of the left rectangle is: 

And the area of the right rectangle is:

The total area of the room is the sum of both rectangles:

The same strategy can be implemented with many other room shapes, even those with round perimeters. Take a look at the following example. The room can be divided into two shapes: a rectangle and a semicircle (half a circle). 

The area of the rectangle is: 

The area of the semicircle is simply half of the area of an entire circle with the same radius. In this case, the radius is 6 ft, which can be extracted by looking at the room’s length (12 ft), which equals the circle’s diameter, and dividing it by two. The area of this section is: 

The total area of the room is then: 

Since many rooms with irregular shapes can be fitted with common shapes as rectangles, triangles or circles, or parts of them, here is a summary of their areas in terms of their main dimensions:

Other helpful sources

If you want to measure the area of a room with an irregular shape, you can use this helpful calculator by HomeAdvisor. Add as many individual shapes as you need to describe the entire space and input their dimensions. Then click “calculate” and see the final result for the room’s area.

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