Cubic Feet Calculator

What the cubic feet calculator does

Cubic feet is the everyday measure of how much space something fills, and working it out by hand means juggling three measurements that are often in different units. This does it for you. You give it a length, a width, and a height, and it returns the volume in cubic feet, with a cost if you add a price per cubic foot.

One number in, the volume out. Below is how it gets there and where the figure is useful.

How to use it

1. Enter the length, width, and height, each with its own unit. They do not all have to match.
2. Add a price per cubic foot if you want a cost, handy for fill materials sold that way.
3. Press Calculate for the volume, or Reset to clear it.

How the volume is worked out

Volume is the three measurements multiplied together, once they are all in the same unit:

Cubic feet = length × width × height

The calculator converts each measurement to feet first, whatever unit you entered it in, then multiplies the three. The cost, if you add one, is that volume times your price per cubic foot.

Mixing units in one go

The useful part is that the three measurements can come in different units, because real measurements often do. A box might be a couple of feet long and wide but only a few inches deep, and a tape gives you whichever is handiest at the time.

So you can enter the length in feet, the width in inches, and the depth in centimeters, and the calculator squares them all to feet before multiplying. That saves the step everyone gets wrong, converting in your head, which is where most volume mistakes creep in.

A worked example: a raised planter

Say you are filling a raised planter that is 4 feet long, 2 feet wide, and 18 inches deep.

The depth in feet is 18 ÷ 12 = 1.5 feet. So the volume is 4 × 2 × 1.5 = 12 cubic feet. If soil costs, say, a dollar a cubic foot, that is a $12 fill.

The mixed units are the point here: the depth came in inches and the rest in feet, and the calculator handled the switch.

Where cubic feet turns up

Cubic feet is the unit for a lot of everyday volumes. Bagged materials like soil, mulch, and concrete mix list their contents in cubic feet, so knowing the volume of the space tells you how many bags to buy. Appliances such as fridges and freezers are sized in cubic feet of interior space, and shipping and storage are often quoted the same way.

So this is the figure you reach for when you need to know how much fits, or how much it takes to fill something. For larger bulk loads measured by the yard, the cubic yards calculator divides this same volume down to that unit.

Questions people ask

How do I calculate cubic feet?

Multiply length by width by height, with all three in feet. A 4 by 2 by 1.5 foot space is 12 cubic feet. The calculator converts the units for you first.

How do I work out cubic feet from inches?

Convert each measurement to feet by dividing by 12, then multiply. Or just enter the measurements in inches and let the calculator do it.

How many cubic feet are in a cubic yard?

Twenty-seven, since a yard is three feet and three cubed is twenty-seven. Bulk materials are often sold by the cubic yard.

How does this help with bags of material?

Bagged soil, mulch, and concrete list their volume in cubic feet, so dividing the space's volume by the bag size gives the number of bags.

References

A quick note on the numbers. The volume is plain geometry, length times width times height. The conversions between inches, feet, yards, centimeters, and meters used to bring every measurement to the same unit follow the US National Institute of Standards and Technology guide, where a foot is defined as exactly 0.3048 meters.

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