October 14, 2022

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

A prism is a crucial figure in geometry. The figure’s name is originated from the fact that it is made by taking into account a polygonal base and extending its sides until it intersects the opposite base.

This article post will discuss what a prism is, its definition, different types, and the formulas for volume and surface area. We will also take you through some instances of how to employ the data provided.

What Is a Prism?

A prism is a three-dimensional geometric figure with two congruent and parallel faces, called bases, which take the shape of a plane figure. The additional faces are rectangles, and their count relies on how many sides the similar 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 characteristics of a prism are interesting. The base and top both have an edge in common with the other two sides, creating them congruent to each other as well! This implies that all three dimensions - length and width in front and depth to the back - can be broken down 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 provided point on any side of this figure'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 regular 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 comprises of two pentagonal bases and five rectangular sides. It looks close to a triangular prism, but the pentagonal shape of the base makes it apart.

The Formula for the Volume of a Prism

Volume is a calculation of the sum of area that an item occupies. As an important figure 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, considering bases can have all kinds of shapes, you will need to know a few formulas to figure out the surface area of the base. Despite that, we will touch upon that later.

The Derivation of the Formula

To derive the formula for the volume of a rectangular prism, we are required to observe 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, assuming,

V = Volume

s = Side length

Now, we will get 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 use it on any type of prism.

Examples of How to Utilize the Formula

Since we understand the formulas for the volume of a pentagonal prism, triangular prism, and rectangular 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, consider 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

Provided that you have the surface area and height, you will figure out the volume with no problem.

The Surface Area of a Prism

Now, let’s talk about 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 important part of the formula; thus, we must learn how to find it.

There are a few different ways to work out 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 use 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 determine the total surface area of a rectangular prism with the ensuing information.

l=8 in

b=5 in

h=7 in

To figure out this, we will plug these numbers 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 Computing 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 same steps as before.

This prism will have 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 data, you should be able to work out any prism’s volume and surface area. Check out for yourself and observe how simple it is!

Use Grade Potential to Improve Your Mathematical Skills Now

If you're having difficulty understanding prisms (or any other math concept, consider signing up for a tutoring class with Grade Potential. One of our experienced teachers can assist you learn the [[materialtopic]187] so you can ace your next test.