by Scott Laughlin
HeyTutor Blog Editor

How to Calculate Square Feet


Square footage is the measurement of space that covers an area. It’s often used to determine the amount of floor space in a home. Knowing the square footage also comes in handy during painting, tiling, and landscaping projects. To find the square feet in a room, you’ll need to calculate the area. Depending on the room’s shape, finding the area might be as simple as multiplying two dimensions. It might also involve a little more complex math. For instance, you can calculate the square footage of a rectangular room by multiplying its length and width (LxW). In contrast, to calculate the square footage of a circular room, you’ll need a different formula (A=πr2). 

Important Note: Before calculating the square feet of any problem, it’s crucial that you first convert the measured dimensions to feet (if they aren’t already in feet). Converting measurements can be done using a few simple rules:

  • To convert from meters to feet, multiply the number by 3.281 (e.g. 10m = 32.81 ft.)

  • To convert from yards to feet, multiply the number by 3 (e.g. 12 yards = 36 ft.)

  • To convert from inches to feet, divide the number by 12 (e.g. 12 inches = 1ft.)

  • To convert from centimeters to feet, multiply the number by 0.03281 (e.g. 1000cm =32.81 ft.)


How to Calculate Square Feet with a Rectangular or Square Room

Calculating the square feet of a rectangular or square area is easy. All it takes is a few quick steps. 

  1. Measure the length of the room

  2. Measure the room’s width 

  3. Convert the linear units to feet (if necessary)

  4. Calculate the area by multiplying the two figures to get the result.

Square feet = L x W

Where: 

L = Length

W = Width

Example

How much square footage is in a rectangular room that spans 4m by 3m? 


Square feet = L x W

First, we need to convert the measurement into feet. 

To convert meters to feet, multiply the number by 3.28

4 x 3.281 = 9.843ft

3 x 3.281 = 13.121ft

Square feet = 129.15 sq. ft. (9.843 x 13.121)

How to calculate Square feet for a Triangular Area

To calculate the square footage for a triangular room or object, solve for its area. The most common approach to calculating the area of a triangle is to multiply half the length of its base by its height (the distance from the base to the highest point in the triangle). 

This is summed up with the formula= 1/2bh (1/2 x b x h). 

Where 

b = length of base in feet

h = height in feet

Example:

Find the area of a 4ft tall triangle with a base that measures 10ft.  

Use the formula 1/2bh (1/2 x b x h).

If the base of a triangle measures 10ft and its height measures 4ft, its total square area will be:
½ x 10 x 4 = 20

Area = 20 sq. ft.

How to calculate Square feet for a Triangular Area Using the Side Lengths

If the base and height of a triangle isn’t known, you can calculate the square footage of a triangular space using the length of its three sides. This is done using Heron’s formula, which states:
Area = √s(s-a) (s-b) (s-c)

Where 

a, b and c = the triangle’s side length 

s = the semi perimeter of the triangle

Example

Find the square footage of a triangular room with sides that measure 11ft, 15ft, and 14ft


Area = √s(s-a) (s-b) (s-c)

s = Perimeter/2

Perimeter = 11 + 15 + 14 =40

S = 40/2 = 20

Area = √20(20-11) (20-15) (20-14)

Area= √20(9)(5)(6)

Area= 73.4847 sq. ft. 

How to Calculate Square Feet for a Circle

Calculate the square footage of a circle by using the formula: A=πr2
Where A = Area of the circle

Π = 3.14159

r = radius (Tip: To find the radius of the room, simply divide the diameter by two). 


Example:

Calculate the square footage of a round room with a 12ft diameter. 

To solve the problem: 

  1. First calculate the radius, which is half the diameter. 12/2 = 6ft.

  2. Next solve for the area using A=πr2  where π= 3.1415

3.1415 x (6)2 =   3.1415 x 36 

Area = 113.094 sq. ft.

How to Calculate Square Feet of an Irregular Shape

To calculate the square footage of an irregular shape, divide the irregular shape into smaller shapes, find the area of each, and then add up all the results. 

Example:

Find the area of the irregular figure below.  


To find the square footage of the area, divide the irregular shape into multiple squares or rectangles, labeled A, B, C, and D. 


Find the Area of A, B, C and D. 

Total Square Foot = Area of A + Area of B + Area of C + Area of D

How is Calculating Square Feet Used in Real Life?

Square footage is used in many professions, including some of the most popular six figure jobs. For instance, software engineers or lawyers looking to expand will rely on square footage when shopping for a new office. Similarly, construction managers who oversee the implementation of new projects use square footage numbers to ensure they have enough materials to finish the project they are working on.


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