How to Calculate the Volume of a Rectangular Prism

Reviewed by Grace Imson, MA

Last Updated: April 25, 2023 Fact Checked

Volume is the amount of three-dimensional space taken up by an object. The computer or phone you're using right now has volume, and even you have volume. Finding the volume of a rectangular prism is actually really easy. Just multiply the length, the width, and the height of the rectangular prism. That's it! This article will walk you through the process step-by-step and show you an example.

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1
Find the length of the rectangular prism. The length is the longest side of the flat surface of the rectangle on the top or bottom of the rectangular prism. ^{[1]
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- Ex: Length = 5 in.
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2
Find the width of the rectangular prism. The width is the shorter side of the flat surface of the rectangle on the top or bottom of the rectangular prism. ^{[2]
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- Ex: Width = 4 in.
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3
Find the height of the rectangular prism. The height is the part of the rectangular prism that rises up. Imagine that the height is what stretches up a flat rectangle until it becomes a three-dimensional shape. ^{[3]
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- Ex: Height = 3 in.
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4
Multiply the length, the width, and the height. You can multiply them in any order to get the same different result. The formula for finding the volume of a rectangular prism is the following: Volume = Length * Height * Width, or V = L * H * W. ^{[4]
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- Ex: V = 5 in. * 4 in. * 3 in. = 60 in.
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5
State your answer in cubic units. Since you're calculating volume, you're working in a three-dimensional space. Just take your answer and state it in cubic units. Whether you're working in feet, inches, or centimeters, you should state your answer in cubic units. ^{[5]
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- 60 will become 60 in ³ .

Calculator, Practice Problems, and Answers

Sample Calculating Volume of a Rectangular Prism Calculator

Sample Calculating Volume of a Rectangular Prism Practice Problems

Sample Calculating Volume of a Rectangular Prism Practice Answers

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Question

If l=45, w=15, h=x, how do I find the volume?

Donagan

Top Answerer

You have to know the height. Otherwise, you'd have to say the volume is 675x cubic units.

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Can you give me another example? I still don't get it.

Community Answer

Remember that length x width x height. A rectangular prism that is five inches high, ten inches long, and two inches deep will have a volume of 100 square in. 5x10x2=100.

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How can I calculate the dimension when I know the volume?

Community Answer

The rectangle's area, times the prism's height vertical to the rectangle, gives the volume; various combinations of dimensions give the same volume, so if you know the volume, and want the dimensions, you will find many sets of dimensions. For example volume 24 could give the length, width, and height of 2, 2, and 6; or 2, 3, 4; or 1, 1, 24; and so on.

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