October 14, 2022

Volume of a Prism - Formula, Derivation, Definition, Examples

A prism is a crucial shape in geometry. The figure’s name is derived from the fact that it is created by taking a polygonal base and expanding its sides until it intersects the opposite base.

This blog post will take you through what a prism is, its definition, different kinds, and the formulas for surface areas and volumes. We will also offer instances of how to use the details provided.

What Is a Prism?

A prism is a three-dimensional geometric figure with two congruent and parallel faces, well-known as bases, which take the form of a plane figure. The other faces are rectangles, and their number relies on how many sides the identical base has. For example, if the bases are triangular, the prism would have three sides. If the bases are pentagons, there will be five sides.


The characteristics of a prism are fascinating. The base and top both have an edge in parallel with the additional two sides, making them congruent to one another as well! This means that all three dimensions - length and width in front and depth to the back - can be deconstructed into these four parts:

  1. A lateral face (meaning both height AND depth)

  2. Two parallel planes which constitute of each base

  3. An illusory line standing upright through any provided point on any side of this figure's core/midline—known collectively as an axis of symmetry

  4. Two vertices (the plural of vertex) where any three planes join

Types of Prisms

There are three main types of prisms:

  • Rectangular prism

  • Triangular prism

  • Pentagonal prism

The rectangular prism is a regular kind of prism. It has six faces that are all rectangles. It matches the looks of a box.

The triangular prism has two triangular bases and three rectangular faces.

The pentagonal prism consists of two pentagonal bases and five rectangular faces. It seems a lot like a triangular prism, but the pentagonal shape of the base stands out.

The Formula for the Volume of a Prism

Volume is a measure of the sum of area that an item occupies. As an essential shape in geometry, the volume of a prism is very relevant in your learning.

The formula for the volume of a rectangular prism is V=B*h, where,

V = Volume

B = Base area

h= Height

Consequently, considering bases can have all sorts of shapes, you are required to retain few formulas to determine the surface area of the base. However, we will go through that afterwards.

The Derivation of the Formula

To derive the formula for the volume of a rectangular prism, we need to look at a cube. A cube is a 3D item with six faces that are all squares. The formula for the volume of a cube is V=s^3, where,

V = Volume

s = Side length

Right away, we will take a slice out of our cube that is h units thick. This slice will make a rectangular prism. The volume of this rectangular prism is B*h. The B in the formula implies the base area of the rectangle. The h in the formula refers to height, which is how thick our slice was.

Now that we have a formula for the volume of a rectangular prism, we can generalize it to any kind of prism.

Examples of How to Utilize the Formula

Considering we have the formulas for the volume of a triangular prism, rectangular prism, and pentagonal prism, now let’s use them.

First, let’s work on the volume of a rectangular prism with a base area of 36 square inches and a height of 12 inches.



V=432 square inches

Now, let’s try another question, let’s figure out the volume of a triangular prism with a base area of 30 square inches and a height of 15 inches.



V=450 cubic inches

Considering that you possess the surface area and height, you will figure out the volume without any issue.

The Surface Area of a Prism

Now, let’s discuss regarding the surface area. The surface area of an item is the measurement of the total area that the object’s surface consist of. It is an essential part of the formula; thus, we must know how to calculate it.

There are a few different ways to work out the surface area of a prism. To measure the surface area of a rectangular prism, you can employ this: A=2(lb + bh + lh), assuming,

l = Length of the rectangular prism

b = Breadth of the rectangular prism

h = Height of the rectangular prism

To work out the surface area of a triangular prism, we will employ this formula:



b = The bottom edge of the base triangle,

h = height of said triangle,

l = length of the prism

S1, S2, and S3 = The three sides of the base triangle

bh = the total area of the two triangles, or [2 × (1/2 × bh)] = bh

We can also utilize SA = (Perimeter of the base × Length of the prism) + (2 × Base area)

Example for Finding the Surface Area of a Rectangular Prism

Initially, we will determine the total surface area of a rectangular prism with the following dimensions.

l=8 in

b=5 in

h=7 in

To figure out this, we will replace these values into the corresponding formula as follows:

SA = 2(lb + bh + lh)

SA = 2(8*5 + 5*7 + 8*7)

SA = 2(40 + 35 + 56)

SA = 2 × 131

SA = 262 square inches

Example for Finding the Surface Area of a Triangular Prism

To calculate the surface area of a triangular prism, we will figure out the total surface area by ensuing identical steps as priorly used.

This prism will have a base area of 60 square inches, a base perimeter of 40 inches, and a length of 7 inches. Thus,

SA=(Perimeter of the base × Length of the prism) + (2 × Base Area)


SA = (40*7) + (2*60)

SA = 400 square inches

With this data, you will be able to calculate any prism’s volume and surface area. Test it out for yourself and see how simple it is!

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