October 14, 2022

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

A prism is an important figure in geometry. The shape’s name is originated from the fact that it is made by taking into account a polygonal base and stretching its sides until it creates an equilibrium with the opposite base.

This blog post will talk about what a prism is, its definition, different kinds, and the formulas for surface areas and volumes. We will also offer examples of how to employ the details provided.

What Is a Prism?

A prism is a three-dimensional geometric shape with two congruent and parallel faces, called bases, that take the form of a plane figure. The additional faces are rectangles, and their count relies on how many sides the identical base has. For instance, if the bases are triangular, the prism would have three sides. If the bases are pentagons, there will be five sides.


The properties of a prism are astonishing. The base and top each have an edge in parallel with the other 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 decrypted into these four parts:

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

  2. Two parallel planes which make up each base

  3. An fictitious line standing upright across any given point on either side of this shape's core/midline—usually 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 kinds of prisms:

  • Rectangular prism

  • Triangular prism

  • Pentagonal prism

The rectangular prism is a common kind of prism. It has six sides that are all rectangles. It resembles a box.

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

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

The Formula for the Volume of a Prism

Volume is a calculation of the sum of space that an thing occupies. As an important shape in geometry, the volume of a prism is very important for your studies.

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

V = Volume

B = Base area

h= Height

Finally, since bases can have all sorts of shapes, you will need to retain few formulas to calculate the surface area of the base. However, we will touch upon that afterwards.

The Derivation of the Formula

To obtain the formula for the volume of a rectangular prism, we need to observe a cube. A cube is a three-dimensional object 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

Immediately, we will have a slice out of our cube that is h units thick. This slice will create a rectangular prism. The volume of this rectangular prism is B*h. The B in the formula stands for 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 use it on any type of prism.

Examples of How to Use 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 work on another problem, let’s work on 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 with no issue.

The Surface Area of a Prism

Now, let’s discuss about the surface area. The surface area of an item is the measure of the total area that the object’s surface comprises of. It is an essential part of the formula; consequently, we must understand how to calculate it.

There are a few distinctive methods to find the surface area of a prism. To figure out the surface area of a rectangular prism, you can utilize this: A=2(lb + bh + lh), where,

l = Length of the rectangular prism

b = Breadth of the rectangular prism

h = Height of the rectangular prism

To compute the surface area of a triangular prism, we will utilize 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 use 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 figure out the total surface area of a rectangular prism with the following data.

l=8 in

b=5 in

h=7 in

To calculate this, we will replace these numbers into the respective 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 compute the surface area of a triangular prism, we will figure out the total surface area by following identical steps as earlier.

This prism consists of a base area of 60 square inches, a base perimeter of 40 inches, and a length of 7 inches. Hence,

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


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

SA = 400 square inches

With this knowledge, you should be able to figure out any prism’s volume and surface area. Check out for yourself and observe how easy it is!

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