How to Easily Calculate Cubic Feet for Any Shape or Object

Calculating cubic feet is a useful skill for shipping, construction, remodeling, and more While it may seem complicated at first, calculating cubic feet is actually quite simple if you know the basic formulas. In this article, I’ll explain step-by-step how to find the cubic feet of any object or space

What is a Cubic Foot?

A cubic foot is a unit of volume equal to a cube with sides of 1 foot. One cubic foot equals 12 inches x 12 inches x 12 inches, or 1728 cubic inches.

In visual terms, a standard refrigerator box is about 1 cubic foot in size. Knowing cubic feet measurements allows you to estimate shipping costs, material quantities needed for construction or landscaping, or the capacity of containers and spaces.

Finding Cubic Feet Using Length, Width & Height

The basic formula for cubic feet is:

Cubic Feet = Length x Width x Height

All measurements must be in feet.

For example, to find the cubic feet of a storage unit that is 10 ft long x 8 ft wide x 6 ft high you would calculate

10 ft x 8 ft x 6 ft = 480 cubic feet

Therefore, this storage unit has a capacity of 480 cubic feet.

This straightforward cubic feet calculation works for any regularly shaped object where you can measure the length, width, and height.

Measuring Irregularly Shaped Objects

For irregular shapes like curved furniture, odd-shaped containers, or unique spaces, you’ll need to break the object down into regular shapes like cubes, rectangles, triangles, and cylinders.

Measure and calculate the cubic feet of each component shape separately, then add them together to get the total cubic feet.

For example, say you want to find the cubic feet of an L-shaped desk:

• The main desk section is 4 ft x 3 ft x 2 ft = 24 cubic feet
• The return section is 2 ft x 3 ft x 2 ft = 12 cubic feet
• Total cubic feet = 24 + 12 = 36 cubic feet

Breaking down irregular objects makes it possible to calculate the cubic feet accurately.

Converting Inches or Meters to Cubic Feet

If you don’t have measurements in feet, you’ll need to convert to feet first before using the cubic feet formula.

• For inches: multiply length x width x height in inches first to get cubic inches. Then divide the cubic inches by 1728 to convert to cubic feet.

• For centimeters: multiply length x width x height in cm first to get cubic cm. Divide the cubic cm by 28317 to convert to cubic feet.

• For meters: multiply length x width x height in meters first to get cubic meters. Multiply the cubic meters by 35.3145 to convert to cubic feet.

Let’s see an example. Say a package measures 12 in x 8 in x 5 in:

• 12 in x 8 in x 5 in = 480 cubic inches
• 480 cubic inches / 1728 = 0.28 cubic feet

So if a package has interior dimensions of 12″ x 8″ x 5″, it would have a volume of 0.28 cubic feet.

Calculating Cubic Feet from Square Footage

If you know the square footage of a floor or other flat surface, you can find the cubic feet if you also know the height.

Use this simple formula:

Cubic feet = Area (square feet) x Height (feet)

For instance, say you have a shed that is 100 square feet in area (10 ft x 10 ft) and the walls are 8 ft high.

To find the cubic feet:

• Area = 100 sq ft
• Height = 8 ft
• Cubic Feet = 100 sq ft x 8 ft = 800 cubic feet

This shed would have an interior capacity of 800 cubic feet.

Finding the Volume of Cylinders

For cylindrical objects like pipes, drums, or silos, you need to use a different formula:

Cubic Feet = (π x Radius2 x Height) / 1728

The radius is half the diameter. π is approximately 3.14.

Let’s calculate the cubic feet of a water storage tank that is 10 feet high with a diameter of 5 feet:

• Radius = Diameter / 2 = 5 ft / 2 = 2.5 ft
• π = 3.14
• Cubic Feet = (3.14 x 2.52 x 10) / 1728 = 98.2 cubic feet

So this cylindrical tank would hold about 98 cubic feet of water.

Real-World Examples

Here are a few real-world examples to illustrate how cubic feet calculations are useful:

• Estimating mulch needs – Say you need to cover a 10 ft x 20 ft flowerbed with 3 inches of mulch. Since mulch depth is usually measured in feet, convert 3 inches to 0.25 ft. Then use the area x height formula:

  • Area = 10 ft x 20 ft = 200 sq ft
  • Height = 0.25 ft
  • Cubic Feet = 200 sq ft x 0.25 ft = 50 cubic feet

• Ordering gravel – You need 11 cubic yards of gravel delivered for a landscaping project. Convert cubic yards to cubic feet by multiplying by 27 (since there are 27 cubic feet in a cubic yard).

  • 11 cubic yards x 27 = 297 cubic feet of gravel needed.

• Shipping costs – You sold a desk on eBay that is 4 ft long x 3 ft wide x 2 ft tall. Calculate cubic feet to estimate shipping costs:

  • 4 ft x 3 ft x 2 ft = 24 cubic feet
  • Check shipping quotes based on a package with dimensions of 24 cubic feet.

• Moving truck rental – You’re moving across the country and need to estimate the size of truck you need. Calculate the total cubic feet of your furniture:

  • Couch – 8 ft x 3 ft x 2 ft = 48 cu ft
  • Bed – 5 ft x 6 ft x 2 ft = 60 cu ft
  • Desk – 4 ft x 3 ft x 2 ft = 24 cu ft
  • Total cubic feet of furniture = 132 cubic feet
  • Rent a truck with at least 150 cubic feet of cargo space.

As you can see, knowing how to quickly calculate cubic feet comes in very handy for all kinds of everyday situations!

Cubic Feet Formulas Cheat Sheet

Here is a quick summary of the important cubic feet formulas covered in this article:

• Basic Volume – Cubic Feet = Length x Width x Height
• Square Footage – Cubic Feet = Area (sq ft) x Height
• Cylinder Volume – Cubic Feet = (π x Radius2 x Height) / 1728
• Inches to Cubic Feet – Cubic Feet = Cubic Inches / 1728
• Cm to Cubic Feet – Cubic Feet = Cubic Cm / 28317
• Meters to Cubic Feet – Cubic Feet = Cubic Meters x 35.3145

Cubic Feet Calculator

To make these cubic feet calculations even easier, use a cubic feet calculator that allows you to input dimensions in feet, inches, yards, meters, etc.

The calculator will handle all the conversions and formulas automatically. Here are two good online cubic feet calculators:

• Inch Calculator Cubic Feet Calculator
• Calculator Site Cubic Feet Calculator

Just enter the required dimensions and the calculator will output the cubic feet measurement.

Knowing how to find cubic feet quickly comes in handy for so many everyday situations from shipping packages to remodeling projects. Next time you need to calculate interior volumes or material quantities, use this step-by-step guide to determine the cubic feet accurately. Our cheat sheet gives you all the formulas you need, or use a cubic feet calculator for convenience.