Figuring out the square footage of a space is an essential skill for home improvement projects, real estate transactions, and space planning. Whether you’re carpeting a bedroom, tiling a bathroom, or buying a home, knowing the square feet helps determine how much material is needed and the potential cost.
Learning how to accurately calculate square footage is simple with just a tape measure, calculator, and the handy formulas below. We’ll walk through the stepbystep process to find the area for rectangular rooms, oddshaped spaces, triangles, and circles. Read on to become a square footage pro!
What is Square Footage?
Square footage refers to the total area of a surface measured in square units, usually square feet or square meters. It tells you how much flat space a surface covers from wall to wall. For example, a 10 ft by 10 ft room has an area of 100 square feet.
Knowing square footage helps with:
 Estimating flooring, paint or tile needed for renovations
 Comparing room and home sizes
 Calculating the cost per square foot of materials
 Visualizing furniture size and layouts for a space
How to Calculate Square Feet: Simple Formula
For rectangular spaces like most rooms, you can easily find the square footage by multiplying the length by the width.
Square footage formula:
Length x Width = Area in square feet
So a room that’s 12 ft long and 15 ft wide is 12 x 15 = 180 sq ft.
Tip: 1 sq ft = a 1 foot by 1 foot square, so imagine stacking those squares to cover the floor space.
Let’s look at how to measure rooms and apply the formula.
How to Measure a Room for Square Footage
Follow these steps to measure a room and calculate the square footage:

Use a tape measure to measure the length of the room from end to end in feet, noting the longest side.

Next, measure the shorter side which is the width in feet.

Multiply the length times the width to get the area in square feet.

Round your final number to a whole square foot.
For example, a bedroom measures 11 ft 6 in long by 9 ft 5 in wide. Convert the inches to feet by dividing by 12 in per foot:
Length = 11.5 ft
Width = 9.4 ft
Area = 11.5 x 9.4 = 108 sq ft
Calculating Square Footage of Irregular Rooms
For irregular shaped spaces, divide the area into separate rectangles and triangles, calculate each piece, and add up the totals.
To find the square feet of a triangle, use:
Length x Width ÷ 2 = Area in square feet
Some examples:

For an Lshaped room, calculate the square footage of each leg of the L separately, then add them together.

For a room with an alcove, measure the main space and alcove separately, calculate both, and combine the totals.

For a pieshaped space, break it into triangles and rectangles that are easier to measure.
How to Find Square Footage of a Triangle
Follow these steps to measure a triangular area and calculate the square footage:

Measure the base of the triangle along the longest side in feet.

Measure the height by drawing a line straight down from the top corner to form a right angle. Measure the height of this line.

Use the formula: Base x Height ÷ 2 = Area in square feet.
For example, for a triangle with an 8 ft base and a 6 ft height:
Area = 8 x 6 ÷ 2 = 24 sq ft
This method works for any triangle. For long skinny triangles, the base is the short side and height is the long side.
Calculating the Square Feet of a Circle
To find the square footage of a circular area like a gazebo or round room, use the formula:
Area = π x (diameter/2)2
Follow these steps:

Measure the diameter across the widest point in feet.

Divide the diameter by 2.

Square the radius number.

Multiply by 3.14 or π.
For example, for a circle with a diameter of 12 ft:
Radius = 12/2 = 6 ft
Area = 3.14 x (6)2 = ~113 sq ft
Use an online calculator if needed for more complex shapes.
Tips for Measuring Square Footage
 For accuracy, measure to the nearest 1/8th inch and convert fractions to decimals before calculating.
 For homes, measure the interior walltowall dimensions rather than exterior.
 Deduct space for fireplaces, bathtubs, and major builtins.
 Don’t subtract for closets – include their area.
 Check your math using an online square foot calculator.
 Add 510% extra when purchasing materials to allow for waste and mistakes.
Applications for Square Footage
Here are just some of the many uses for square footage calculations:

Flooring: Determine how much tile, carpet, or wood flooring is needed.

Painting: Estimate the number of paint gallons needed based on square feet of wall space.

Furniture shopping: Use the square footage and layout of a room to select appropriately sized beds, sofas, or shelving units.

Rugs and mats: Calculate dimensions for area rugs, bathmats, and door mats.

Building materials: Calculate materials needed for siding, roofing, decking etc.

Lawn care: Determine how much sod, fertilizer, mulch etc. is required.

Real estate: Compare home and room sizes and determine price per square foot.

Space planning: Visualize furniture arrangements and traffic flow based on square footage.
So now you can accurately measure and calculate the square feet of any regular, irregular, or round space. Knowing how to find square footage gives you a handy skill for home projects, and helps you make the most of the area you have to work with.
Why Calculating Square Footage is Important
Knowing how to calculate the square footage of a home is a very beneficial skill to have in the process of home building and will come in handy in many scenarios, including
 Determining the real estate value of your home: Square footage is a key factor in determining the value of a home. Should you ever choose to sell your home, this information will be crucial for appraisers, buyers, and real estate agents.
 Buying and installing flooring: When it comes time to buy flooring (or make renovations), you will need the square footage of the area you are working on in order to buy the correct amount of materials.
 Paying property taxes: If you live in an area where real estate property taxes are assessed based on the square feet of a house, knowing the number will help ensure that you are paying the correct amount in property taxes.
 Obtaining building permits: In most areas, you will typically need to submit plans that show the square footage of your home in order to obtain a building permit.
 Purchasing insurance: You will need to provide the square footage of your home to insurance companies for the majority of policies. This information is also used to determine the cost of your premium.
 Home improvement projects: If you eventually decide to add an addition onto or update your house, you will need to know the sq ft. This information will be especially useful if you go the “diy” route and make renovations yourself, without the help of a professional.
Tips for calculating the square footage of an irregular shape:
 When dividing the room into multiple shapes, make sure that the shapes are completely enclosed and that there are no gaps between them.
 When calculating the total area of each shape, round each number to the nearest square foot.
To measure the sq. ft of a rectangular room, follow these steps:
 Measure the length of the room by starting at one corner of the room and extending the tape measure to the opposite corner. Record the measurement in feet.
 Measure the width of the room by starting at the same corner where you measured the length and extending the measuring tape to a different corner on the same wall. Record the measurement in feet.
 Multiply the length by the width to calculate the square footage.