Sq. Foot Calculator
Use this calculator to work out an area of square feet, square meters or square yards for flooring, landscaping, carpets, garden or construction projects.
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- Square footage formula
- How to calculate square feet
- How to calculate the sq. ft of a rectangle
- Calculations for ‘L’ shaped areas and rooms
- How to calculate the sq. ft of a triangle
- How to calculate the sq. ft of a circle
- How to calculate the square footage of a house
- How many square feet is a 20×20 room?
- How many square feet is a 12×12 room?
Square footage formula
The formula for calculating the square footage of a rectangular area, room or house from measurements in feet is:
Square footage = Length (feet) × Width (feet)
If the area or room you’re measuring is not a rectangle, we’ll go through instructions for different shaped areas below – including ‘L’ shapes.
We’ll start with the basic method for how to measure and calculate square footage for common room or area shapes. Before we do this, it’s important to touch on units. For these calculations to work, your measurements need to be in feet. If they aren’t in feet already, you’ll need to convert them as follows:
- For measurements in inches: divide by 12 for feet
- For measurements in yards: multiply by 3 for feet
- For measurements in cm: divide by 30.48 for feet
- For measurements in m: multiply by 3.281 for feet
How to calculate square feet
For a square or rectangular shaped room or area, measure the length and width of the area in feet. Then, multiply the length and width figures together. As an example, if your room measures 14 feet wide by 18 feet long, your calculation is 14 × 18 = 252 square feet.
To calculate an area in square feet, you will need to take measurements for the width and length (for a rectangular shape), or the diameter (for a circular area).
It may be that the area you’re looking to measure is an unusual shape, such as an L-shape. In this instance, dividing the area up into smaller parts and doing individual calculations makes calculating the overall square footage easier. We’ll discuss how to do this further down the article.
Once you’ve calculated your square footage measurement, you may wish to calculate cubic yard volume for bulk materials such as mulch or gravel.
How to calculate the sq. ft of a rectangle
Measure the width and length of the rectangular area in feet. Next, multiply the length and width together to get the area. Length (feet) × width (feet) = area of rectangle in square feet.
Example of calculating sq. ft for a rectangular room
Let’s say that we’re measuring for new flooring for our living room. We’ve measured the room and found that it is 16 feet long and 12 feet wide. To calculate the square footage of our living room we multiply these two figures together: 16 × 12 = 192 square feet. We now know that we’ll need 192 square feet of flooring.
Note: If your measurements aren’t in feet, you can convert them to feet first using our length conversion tool.
Calculations for ‘L’ shaped areas and rooms
Should you find yourself needing to calculate an area of square feet in an ‘L’ shape, divide the shape up into rectangular sections and treat each one as a separate area for calculation. You can then add the totals together at the end.
It’s worth noting that we have a step-by-step guide for how to measure and calculate square footage.
In the example above, we have divided our ‘L’ shaped room up into two sections. The first section measures 6ft × 5ft = 30 square feet. The second section measures 14ft × 10ft = 140 square feet. Adding the two figures together we find that our room measures 30+140=170 square feet.
How to calculate the sq. ft of a triangle
- Measure the length and the width of the triangle in feet.
- Multiply your length and width measurements together.
- Divide your total by two to get the square footage of the triangle
The formula for calculating the square footage area of a triangle is: length × width / 2. If you need to work out the cost of materials for a triangular area, simply multiply the square feet figure by your ‘price per square foot’.
In our above example, our triangular area has a length of 16ft and a width of 12 ft. To calculate the square footage we multiply 16 × 12 and then divide it by 2. Our calculation: 16 × 12 / 2 = 96 square feet.
How to calculate the sq. ft of a circle
- Measure the diameter of your circle in feet.
- Divide your diameter by 2 and then square it (multiply it by itself).
- Multiply your total by π (3.14159265)
The formula for calculating the area of a circle is: π r 2 (with r being the radius of the circle, which is half the diameter). π is the symbol for pi (3.14159265).
In our above example, our circular area has a diameter of 16ft. To calculate the square footage we divide our diameter in half, multiply the resulting figure by itself and then multiply it by π. Our calculation: π × (16 × / 2)² = 201 square feet.
How to calculate the square footage of a house
If your house is a perfect rectangle then you can calculate the square footage by measuring the width and length of the house and multiplying the two figures together. This will give you the square footage of each floor. If your house has more than one floor, you can multiply this figure by the number of floors.
If your property is a more complex shape, consider drawing out a floor plan of each level of your house. You can then separate each floor off into individual shapes, taking measurements for each room. Here’s a video example.
The average size of a single family house in the United States is 2,261 square feet, according to Statistica. 1
How many square feet is a 20×20 room?
The square footage of a room measuring 20 feet wide by 20 feet long is 400 square feet. This is calculated by multiplying the width by the height. 20ft × 20ft = 400 sq ft.
How many square feet is a 12×12 room?
The square footage of a room measuring 12 feet wide by 12 feet long is 144 square feet. This is calculated by multiplying the width by the height. 12ft × 12ft = 144 sq ft.
Summary of calculations
Below is a summary of what we’ve covered.
|Room or area shape||Sq. ft Calculation (in feet)|
|Rectangle||Width × Length|
|L-shape||Split the area or room into separate rectangles and measure each separately|
|Triangle||Length of base × Height / 2|
|Circle||π × [Diameter / 2]²|
If you want to work out a cubic feet volume based upon your square feet figure, you can try our square feet to cubic feet calculator. For further assistance with measuring and calculating square feet for a room or house, check out our step-by-step guide.
And, if you’re measuring land, we have a handy tool to help you convert between acres and square feet.
- Statistica. Median size of single family housing unit in the US from 2000 to 2023.
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