Square Footage Calculator
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How to calculate square feet
To calculate an area in square feet, you will need measurements for the width and length (for a square shape) or the diameter (for a circular area). It may be that the area you're looking to measure is a strange shape (such as a room or garden). In this case, dividing it up into smaller parts and doing individual calculations is a good way to calculate the overall square footage.
Let's say you have a rectangular-shaped room and you want to calculate the square footage area for flooring or carpet. The easiest method for calculating the square footage is to measure the length and width in feet and then multiply the two figures together to give you a result in ft2. If you're measuring a room for flooring, take a look at our article on how to measure for a new floor.
Should you find yourself needing to calculate an area of square feet in an 'L' shape, consider dividing the shape up into rectangular sections and treating them as separate areas for calculation (adding them together at the end). For more instructions, see our full article: how to calculate square footage.
Making the calculations
- For a square or rectangular area, measure the Width and Length in feet.
- Multiply your Length × Width to get your area.
Note: If your measurements aren't in feet, convert them to feet first using the instructions below or the length converter.
- If in inches: divide each figure by 12 to get feet measurement.
- If in yards: multiply each figure by 3 to get feet measurement.
- If in cm: multiply each figure by 0.03281 to get feet measurement.
- If in m: multiply each figure by 3.281 to get feet measurement.
Once you've carried out your calculation, you will have your square feet (ft2) figure. To calculate your cost of materials, simply multiply this figure by your price per square foot. For other area shapes (circles, triangles), instructions and formulae are below. If you would like to convert your figure into cubic feet, take a look at the square feet to cubic feet calculator.
Of course, it may be that the area you're measuring isn't rectangular. Instructions on calculating for a circular area and triangular area are further down.
How many square feet is a 20x20 room?
The square footage of a room measuring 20 feet wide by 20 feet long is 400 square feet. To calculate this you simply multiply the width by the height. 20ft × 20ft = 400 sq ft.
How many square feet is a 12x12 room?
The square footage of a room measuring 12 feet wide by 12 feet long is 144 square feet. To calculate this you simply multiply the width by the height. 12ft × 12ft = 144 sq ft.
Square footage for a circular area
- Measure the diameter of your circle in feet.
- To calculate the area of a circle we use the formula: π x (diameter/2)2. That is to say π (pi is 3.14159265) multiplied by half the diameter squared. So, we divide our diameter by 2 and then square it (multiply it by itself) and then multiply by π.
- This gives you your square feet figure (ft2). To work out your cost of materials, simply multiply this figure by your 'price per square foot'.
The formula for calculating the area of a circle is: π r2 (with r being the radius of the circle, which is half the diameter). π is the symbol for pi (3.14159265).