Square Feet to Cubic Yards Calculator

What the square feet to cubic yards calculator does

Slabs and beds are measured as an area, in square feet, but concrete and gravel are ordered by the cubic yard, so somewhere between the tape and the supplier the units have to change. This bridges them. You give it an area and a depth, and it returns the cubic yards, or you can run it backwards from cubic yards to an area.

It is the step between the size of a pour and the amount you order. Below is how it works and why the depth carries the whole thing.

How to use it

1. Pick the direction: square feet to cubic yards, or cubic yards back to square feet.
2. Enter the area or volume, whichever your direction starts from.
3. Enter the height or depth with its unit, then press Calculate, or Reset to clear it.

How the conversion works

An area becomes a volume when you give it a depth, and cubic yards just measures that volume in a bigger unit. The calculator multiplies the area by the depth and scales the result down to yards:

Cubic yards = area in square feet × depth, brought to cubic yards

It converts the depth you enter into yards first, then combines it with the area so the answer lands in cubic yards. Run the other way, it works back from a volume to the area that volume would cover at the depth you give.

Why the depth is the key

An area on its own holds no volume, so the depth is what makes the conversion possible at all. A driveway is the same number of square feet whether you pour two inches of concrete or six, but the cubic yards differ hugely between them, and so does the bill.

That makes the depth the figure to get right, and the one people most often leave loose. A slab at four inches needs twice the concrete of the same slab at two inches, so it is worth setting the depth to exactly what you are pouring, since the cubic yards ride entirely on it.

Going both directions

The reverse direction, cubic yards back to square feet, has its uses. If a load of concrete or gravel is already on order, you can work out how far it will spread at a given depth, which tells you whether it will cover the area you have in mind, or leave you short.

So one direction answers how much to order for a space, and the other answers how much space a load will cover. Both rest on the same relationship between area, depth, and volume, solved for whichever piece you are missing.

A worked example: a concrete slab

Say you are pouring a 100 square foot slab, 4 inches thick.

Four inches is a third of a foot, so the volume is 100 × 0.33 = 33 cubic feet, which works out to about 1.23 cubic yards. That is the figure you would give the concrete supplier.

For a real pour it is worth ordering a touch over, since a slab that runs short cannot be paused while more is mixed.

Questions people ask

How do I convert square feet to cubic yards?

Multiply the area by the depth to get a volume, then bring it to cubic yards. A 100 square foot slab at 4 inches deep is about 1.23 cubic yards.

Why do I need the depth?

Because an area has no volume until it has a thickness. The same slab needs twice the concrete at twice the depth, so the depth sets the answer.

How many cubic yards of concrete do I need?

Enter the slab's area and thickness and the calculator gives the cubic yards. Order a little extra, since a short pour cannot be topped up partway.

Can I go from cubic yards back to square feet?

Yes. Divide the volume by the depth to find the area it covers, useful when a load is already on order.

References

A quick note on the numbers. The conversion is plain geometry: an area times a depth is a volume, and a cubic yard is 27 cubic feet, since a yard is three feet in each direction. The unit conversions used to bring the depth to a common unit follow the US National Institute of Standards and Technology guide.

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (SI). https://www.nist.gov/pml/special-publication-811