Calculate the Volume of a Rectangular Tank in Gallons

Volume of a rectangle (V, cu ft) = (length, ft) x (width, ft) x (height, ft), then convert cubic feet to gallons (1 cubic foot = 7.48 gallons)

If you have a rectangular shaped storage tank there is a very simple calculation that can give you the number of cubic feet that will fit inside of that rectangle. Once you have that number you can covert those cubic feet to gallons to know how many gallons of water your tank holds. Here is the formula:

(V, cu ft) = (L, length, ft) x (W, width, ft) x (H, height, ft)

This will give you the volume in cubic feet, which can be converted to gallons (1 cubic foot = 7.48 G, gallons) by taking (cu ft, cubic feet) x (7.48, number of gallons per cubic foot)


V = Volume

L = Length

W = Width

H = Height

cu ft = Cubic Feet

G = Gallons


More information related to Calculate the Volume of a Rectangular Tank in Gallons:


The volume of anything is simply how much space that object takes up. It has many applications, like determining how much water will fit inside a tank or a pipe with certain dimensions. The volume is often calculated by first determining the area of one plane of an object (e.g. its footprint) and multiplying that area by the final dimension (in many cases this is the object's height). So, if we imagine a standpipe that is 20 feet across (radius = 10 feet), we know that the area of the standpipe's footprint is Pi x 10 x 10 = 314 square feet.

Now, to calculate how much that standpipe can hold, we must multiply our area by the height. In this case, our standpipe is 100 feet tall so the calculation is easy: Volume = 314 square feet x 100 feet = 31,400 cubic feet. Often, this measurement would then be converted into liters.

Remember in your equation to use a calculator to calculate Pi.

Volume Conversions

Volume conversions are among the most common conversions made in drinking water operations. As an operator, you will commonly be expected to know the difference, and convert, between mL, L, cups, gallons, cubic feet, cubic meters, and many others. The secret is not to memorize each and every conversion, but to first have an idea of the relative size of the units (i.e. cups are smaller than liters) and then know where to look up the exact conversion numbers. It certainly helps to have an idea of relative sizes (i.e. there's a bit more than 4 cups in a liter), but it isn't necessary if you just know where to look. Keep a chart of relative volumes so you can quickly convert between any unit you may encounter.

The Calculate the Volume of a Rectangular Tank in Gallons slide is featured in the following lessons:

Storage Facilities

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