Square Feet and Cubic Feet
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Square feet to cubic feet formula
The formula for calculating a cubic feet volume from a square feet area is:
Cubic feet = Square feet × Height in feet
If your height or depth is in inches, your formula looks like this:
Cubic feet = Square feet × Height in inches ÷ 12
How to convert square feet to cubic feet
To calculate cubic feet from square feet, multiply the square footage of your object or area by the depth or height. This assumes that the height measurement is in feet. If it isn't, you'll need to convert it to feet first.
The square foot is a unit of area (two dimensions) and is commonly calculated by multiplying width and length together. The cubic foot is a unit of volume (three dimensions) - commonly calculated by multiplying width, length and height measurements together. This means that it is not a conversion as such, as we are not comparing like for like - one has two dimensions, the other has three.
To calculate cubic feet based upon a square feet figure requires us to know an extra dimension: height/depth. You could, in theory, fit many different measurements of square feet into a cubic foot. Picture a swimming pool - it could be very long, wide and shallow. Or, it could be shorter in length and width and be very deep. Both of these swimming pools could, in theory, have the same cubic feet volume. But, their surface area would be very different.
Here's an example of two boxes, both measuring 6 cubic feet.
Your reasons for wanting to calculate cubic feet from a square feet figure may vary. One common reason is for landscaping. You might want to buy mulch or topsoil for your garden - these materials are commonly sold in cubic feet or cubic yards.
Example calculation
Let's say you have a garden measuring 20 square feet, and you want to cover it in 3 inches of topsoil. The topsoil you want is sold by the cubic foot, so we need to do a conversion and calculation.
- Convert our depth figure from inches to feet (so that units are the same). There are 12 inches in a foot. 3 ÷ 12 = 0.25 ft.
Our topsoil depth is 0.25 ft. - Cubic feet = square feet × depth.
So: 20 × 0.25 = 5. - We have our total:
5 cubic feet.
Cubic feet to square feet formula
The formula for calculating square feet from a cubic feet figure is:
Square feet = Cubic feet ÷ Height in feet
How to convert cubic feet to square feet
To calculate the square footage area of an object or volume, divide your cubic feet figure by one of the dimensions - commonly the height. To make this calculation work, your height figure needs to be in feet.
As we discussed earlier in our article, it is important to note that this is not a conversion as such, due to the fact that a cubic foot is a unit of volume (three dimensions) and a square foot is a unit of area (two dimensions). So, you're not comparing like for like. In order to calculate how many square feet of area there are in your cubic feet of volume, you need to know the measurement of one of the dimensions, in feet.
In our calculator, above, we've stated this as 'height', but it could equally be length or width, depending on which side of the object you're trying to measure. Once you have one of the dimensions, your calculations can be carried out using the formulae below.
Note: this formula assumes all measurements are in feet.
Cubic feet to square feet formula
Example calculation
Using our topsoil example above, and working backwards, you'll see how it works. As a reminder, we have 5 cubic feet of top soil and a depth of 0.25 feet (3 inches). What is the square feet measurement?
- Square feet = cubic feet ÷ depth.
So: 5 ÷ 0.25 = 20. - We have our total:
20 square feet.
Of course, if you use our calculator at the top of the page, it'll work these calculations out for you.
Calculator by Alastair Hazell Last updated: August 2, 2023If you have any problems using our square feet and cubic feet calculator, please contact us.