Cubic Yards Calculator

What the cubic yards calculator does

The cubic yard is the unit the big stuff comes in: concrete, soil, gravel, and mulch are all ordered by the yard. This works out how many you need. You give it a length, a width, and a depth, and it returns the volume in cubic yards, with a cost if you add a price.

It is the unit that decides what you tell the supplier. Below is how it works and why the yard rules the bulk yard.

How to use it

1. Enter the length, width, and depth, each with its own unit, mixed however your measurements come.
2. Add a price if you want a cost estimate.
3. Press Calculate for the volume in cubic yards, or Reset to clear it.

How the volume is worked out

It multiplies the three measurements for the volume, then divides by 27 to put it in cubic yards:

Cubic yards = (length × width × depth) ÷ 27

The calculator converts each measurement to feet first, multiplies them to get cubic feet, then divides by 27 to reach cubic yards. The cost, if you add one, is the cubic yards times your price.

Why everything gets divided by 27

The 27 catches people out, because it feels like it should be 3. The reason it is not is that a yard is three feet in each of three directions. A cubic yard is a cube three feet long, three feet wide, and three feet tall, and three times three times three is 27. So one cubic yard holds 27 cubic feet.

That is why a slab that sounds modest in feet shrinks to a small number of yards. The volume in cubic feet is the same amount of material; the yard is just a bigger bucket to measure it in, which is what makes it handy for loads too large to count in cubic feet.

A worked example: a concrete slab

Say you are pouring a slab 10 feet by 10 feet, 4 inches thick.

The thickness in feet is 4 ÷ 12 = 0.33 feet. So the volume is 10 × 10 × 0.33 = 33.3 cubic feet, and dividing by 27 gives about 1.23 cubic yards.

That is the figure you would give the concrete supplier, though for a real pour it is worth ordering a touch over, since you cannot stop halfway to fetch more.

Why bulk materials use the yard

Bulk materials are sold by the cubic yard for the same reason you buy rice by the bag and not the grain: it is the right size unit for the quantity. A driveway's worth of gravel or a foundation's worth of concrete runs to many cubic feet, and counting it in yards keeps the numbers manageable for both you and the supplier.

It also matches how the material is delivered, by the truckload or the scoop, both measured in yards. So when you are pricing concrete, soil, gravel, or mulch, the yard is the number that matters, and this turns your measurements straight into it.

Questions people ask

How do I calculate cubic yards?

Multiply length by width by depth in feet, then divide by 27. A 10 by 10 foot slab 4 inches thick is about 1.23 cubic yards.

How many cubic feet are in a cubic yard?

Twenty-seven, because a cubic yard is three feet in each direction and three cubed is 27.

How many cubic yards of concrete do I need?

Work out the volume of the pour in cubic feet and divide by 27. Order a little extra, since a short pour cannot be paused to top up.

Why enter depth in inches?

Because slabs and fills are usually a few inches deep, not feet. The calculator converts the inches to feet before working out the volume.

References

A quick note on the numbers. The volume is plain geometry, length times width times depth, and the division by 27 comes straight from a yard being three feet, so a cubic yard is three cubed cubic feet. The unit conversions used to bring each measurement to feet 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