Average of Three Numbers in C

Calculating the Calculate Average of Three Numbers in C is a common operation in many programming scenarios. In the context of the C programming language, finding the average of three numbers involves summing those numbers and then dividing the sum by the number of numbers, which is three in this case. For beginners, this task serves as a practical way to apply basic math in code and helps to familiarize them with the syntax of C. We use variables to store data, operators to perform arithmetic, and the print function to display results. In this tutorial, we will learn how to find the sum and average of three numbers using C programming language. We will use the formula sum / 3.0 to calculate the average of the numbers, where sum is the total of the three numbers entered by the user.

Working with C to accomplish this helps solidify understanding of data input and output, the use of variables, and arithmetic operations. The formula to find the average is straightforward: average = (sum of numbers) / (count of numbers). Thus, if we want to calculate the average of three numbers, we add them together and then divide by three. It’s a simple concept, but it serves as the foundation for more complex programming tasks.

average of three numbers in c
average of three numbers in c

Key Takeaways

  • We employ variables to store the sum and average, and the arithmetic ‘+’ and ‘/’ operators to perform calculations.
  • The function printf is used to output the average to the screen, displaying the result of our program.
  • Understanding how to calculate an average in C reinforces fundamental programming concepts and prepares us for more advanced topics.

Understanding the Basics

In this section, we dive into the fundamental aspects of calculating averages in C programming. We’ll clarify the concept of an average, outline the different data types in C, and briefly touch on the basics of C programming language for a strong foundational understanding.

What Is an Average

An average is a number expressing the central or typical value in a set of data, calculated as the sum of the numbers divided by the count of numbers. When we talk about the average of three numbers, we are referring to the sum of these numbers divided by three. This is a basic arithmetic operation and an essential algorithm in many programming tasks.

Data Types in C

In C programming, a data type specifies the type of data that a variable can hold. The two primary data types used for numerical values are:

  • int: stands for integer, used to represent whole numbers without a decimal point.
  • float: stands for floating-point number, used to represent numbers that may have a fractional part.

To store the values of the numbers we wish to find the average of, we declare three float variables if we want to support decimal averages, or int variables if we only want to calculate the average for whole numbers.

The C Programming Language Basics

C is a robust programming language that requires us to define variables and their data types before we use them in calculations. For example:float num1, num2, num3, average;

Here, num1num2num3, and average are the names of our variables. The float in front indicates that these variables can hold numbers with decimal points. Once these variables are declared, we can use them to store our numbers and calculate their average like so:average = (num1 + num2 + num3) / 3.0;

The division by 3.0, a float, ensures that we get a float result, preserving any decimal values. Always remember that C requires explicit declarations, which helps us avoid mistakes and clarifies our code to others reading it.

Setting Up the Environment

Before we start writing a C program to calculate the average of three numbers, we need to ensure that our environment is properly set up. This entails installing a C compiler and understanding the basic structure of a C program.

Installing C Compiler

To compile and run a C program, we require a C compiler. A C compiler is a software that translates the C code we write into machine language so that our computer can execute it. Here’s how to install a C compiler:

  • On Windows: We can download and install MinGW (Minimalist GNU for Windows). MinGW provides a complete Open Source programming tool set, of which GCC (GNU Compiler Collection) is an essential component for compiling C programs.
    • Go to the MinGW website to download the installer.
    • Run the installer and select the mingw32-gcc-g++ package.
    • Follow the instructions to install.
  • On macOS: The Clang compiler is usually pre-installed. We can access it through the Terminal.
    • Open the Terminal.
    • Type gcc --version to check if the compiler is installed.
    • If not, we install the Xcode Command Line Tools by typing xcode-select --install.
  • On Linux: GCC is usually pre-installed.
    • Open the Terminal.
    • Type gcc --version to verify it’s installed.
    • If it’s not, we can install it via the package manager. For example, on Ubuntu, we would run sudo apt install build-essential.

Basic Program Structure

A basic C program structure includes the following:

  • Preprocessor Commands: These commands tell the compiler to include information from external files. For instance, #include allows us to use input and output functions like printf() and scanf().
  • Main Function: Every C program must have a main() function. It is the entry point of the program and the execution starts from here.
  • Variable Declarations: Here, we declare the types of data that will be used in the program. For example, int number; declares an integer variable named number.
  • Body of the Function: This section contains the execution statements of the program. It’s where we write the logic of our program.
  • Return Statement: Typically, return 0; signifies that our program has executed successfully.

By understanding these components, anyone, including a layman new to programming, can set up their environment and start coding in C. This setup is unrelated to web development stacks such as full-stack JavaScript development with frameworks like Angular, React, or backend technologies like Node.js with Express and databases like MongoDB. We’re focused on the essentials specific to running a simple C program.

Writing the Program

To begin writing our C program to calculate the average of three numbers, we’ll focus on three key sections. We’ll start by declaring our variables, then we’ll move on to reading the user’s input using the scanf() function, and lastly, we’ll compute the average with a dedicated function.

Declaring Variables

In any program, the first step is always to declare variables to store data. In our case, we need to hold three numbers and the average.

float number1, number2, number3, average;

Here, we have declared four variables of float type. The float keyword specifies that our variables can hold numbers with decimal points, which is crucial for calculating an average that may not be an integer.

Reading Input Using Scanf()

To obtain values from users, we use the scanf() function. This function reads formatted input from the standard input, typically the keyboard.

printf("Enter three numbers: "); 

scanf("%f %f %f", &number1, &number2, &number3);

In the scanf() function, %f is used as a placeholder for float values. The & symbol before each variable name is necessary because scanf() needs the address to store the input data.

Calculating Average of Three numbers in C with a Function

Once we have our inputs, we can calculate the average. Let’s create a function called calculateAverage:

float calculateAverage(float num1, float num2, float num3) {
return (num1 + num2 + num3) / 3;

This function takes three float arguments and returns a float value. In the return statement, the sum of num1num2, and num3 is divided by 3 to find the average, which is then stored in the avg variable. This result is then provided back to where the function was called in our program. When we call this function, we’ll use the variables we obtained from the user as input numbers.

average = calculateAverage(number1, number2, number3);

Using a function like this modularizes our code, making it easier to read, maintain, and use elsewhere if needed. We then output the result, potentially formatting it to a specific number of decimal places, ensuring that our output is both accurate and user-friendly.

Displaying the Result

When we talk about displaying the result in a C program, we’re focusing on how we present the calculated average to the user. This presentation of data typically happens in the program’s output window.

Using Printf() Function

The printf() function is a standard library function that allows us to send formatted output to the screen (or the output window). Here’s how we use it step by step:

  1. We begin with the printf() function followed by parentheses () which is how we tell the program we want to print something.
  2. Inside the parentheses, we write our message in double quotes \". Anything inside these quotes will be shown to the user.
  3. Within the message, we use format specifiers such as %d for integers or %f for floating-point numbers. These serve as placeholders for the values we want to display.

For example, if our calculated average is a variable named avg, we’d use:printf(“The average is: %f”, avg);

Here %f is a placeholder for our floating-point number, which is the average in this case.

Handling Decimal Points

Handling decimal points is crucial for providing accurate results, especially when dealing with averages. We often want to control the number of decimal points displayed in the output window. This is where printf() shines with its ability to format the output:

  1. Again, we use the printf() function, which sends our formatted text to the output window.
  2. Inside the format specifier, we use a period . followed by the number of decimal points we want. For example, %.2f means we want to display the number with two decimal points.
printf("The average is: %.2f", avg);

In this line of code, %.2f tells the program to display avg as a floating-point number rounded to two decimal places. The % signifies the start of the format specifier, the . signals that precision is being set, and the 2 indicates we want two digits after the decimal point, rounded if necessary. The f stands for floating-point number, which can handle decimal values.

Advanced Concepts and Practices

In our exploration of advanced concepts, we’ll examine efficient strategies for calculating the average of three numbers using arrays and code optimization techniques.

Arrays and Average Calculation

Arrays in C offer a structured way to store multiple items of the same type. For the task of averaging numbers, we can use an array to hold the three values. This approach not only simplifies the declaration of variables but also streamlines the loop-based implementation of the calculation.

Let’s consider an example:

#include <stdio.h>

int main() {
    // Declare an array of type float to store the three numbers
    float numbers[3];
    float sum = 0.0, average;

    // Input the three numbers
    printf("Enter three numbers: ");
    for(int i = 0; i < 3; i++) {
        scanf("%f", &numbers[i]);
        sum += numbers[i]; // Add each number to the sum

    average = sum / 3.0; // Calculate average by dividing the sum by 3.0
    printf("Average is: %.2f", average);

    return 0;

In this code:

  • We use the float type to allow for floating-point numbers, which can represent real numbers (including fractions).
  • Our array numbers is initialized to hold three float values.
  • The for loop iterates over each element in the array, summing the elements.
  • The average is computed by dividing the total sum by 3.0, which accurately calculates the average as a float instead of an integer.

Optimizing the Code

When it comes to optimization, we can refine our code for performance and readability. Consider the practice of function usage to separate the logic of averaging numbers from the main body of the code.

The tutorial for this optimization could look something like this:

#include <stdio.h>

// Function declaration
float calculateAverage(float numbers[], int size);

int main() {
    float numbers[3] = {0};
    float avg;

    printf("Enter three numbers: ");
    for(int i = 0; i < 3; i++) {
        scanf("%f", &numbers[i]);

    // Function call
    avg = calculateAverage(numbers, 3);
    printf("Average: %.2f", avg);

    return 0;

// Function definition
float calculateAverage(float numbers[], int size) {
    float sum = 0.0;

    for(int i = 0; i < size; i++) {
        sum += numbers[i];

    return sum / size;

In this example, we have:

  • function calculateAverage that takes an array of float numbers and the size of the array as arguments.
  • It returns the average as a float after performing the calculation.
  • This provides a simple way to reuse the averaging logic in different parts of our program or in future programs.

These are the practice examples that illustrate how to handle the task of averaging three numbers by implementing arrays and optimizing code structure, which can be incremental steps to mastering C programming.

Frequently Asked Questions

When working with C programming, thoroughly understanding how to manipulate and calculate numerical values is essential. In this section, we’ll address some common queries related to computing the average of three numbers in C.

How can I write a C program to calculate the average of three numbers?

To calculate the average of three numbers in C, we initialize three variables to store the numbers and another to hold the average. Then, we use the arithmetic mean formula to calculate the average.


  1. Declare three float or int variables abc.
  2. Prompt the user to input values and store them using scanf.
  3. Declare a fourth variable to store the average, say avg.
  4. Calculate the average: avg = (a + b + c) / 3;.
  5. Use printf to display the result, optionally formatting it for decimal places.

This basic structure allows you to efficiently calculate the average of three numbers in C.

Why is it important to use float for storing numbers in this program?

The choice between using float or int depends on whether you want to include decimal points in the average. If you want a more accurate average that considers fractional values, float is suitable. If you only need the average as an integer (whole number), int can be used.

For example:float num1, num2, num3, average; // Use float for potential decimal averages

Or:int num1, num2, num3, average; // Use int for whole number averages

By selecting the appropriate data type, you ensure that the program behaves as intended and produces accurate results.

How can I modify the program to calculate the average of more than three numbers?

To modify the program to calculate the average of more than three numbers, you can make use of arrays to store the input values. Instead of declaring individual variables for each number, declare an array and use a loop to input values. Then, calculate the average as before.

Here’s an example that calculates the average of five numbers:#include <stdio.h> int main() { int count; printf(“Enter the count of numbers: “); scanf(“%d”, &count); float numbers[count]; float sum = 0.0, average; printf(“Enter %d numbers: “, count); for(int i = 0; i < count; i++) { scanf(“%f”, &numbers[i]); sum += numbers[i]; } average = sum / count; printf(“Average is: %.2f”, average); return

This example uses a loop to input an array of numbers based on the user-specified count, allowing the program to calculate the average of any desired number of inputs.

Can I calculate the average without using a separate function?

Yes, it’s possible to calculate the average without using a separate function. In the examples provided earlier, the function calculateAverage was introduced to demonstrate modularization and code organization. However, for a simple program like calculating the average of three numbers, a separate function is not strictly necessary.

The main calculation can be performed directly within the main() function. Here’s an example without a separate function:#include <stdio.h> int main() { float num1, num2, num3, average; printf(“Enter three numbers: “); scanf(“%f %f %f”, &num1, &num2, &num3); average = (num1 + num2 + num3) / 3.0; printf(“The average is: %.2f”, average); return

This approach is suitable for small programs where the logic can be easily contained within the main()function. As programs grow in complexity, using separate functions becomes a good practice for code readability and maintainability.


Calculating the average of three numbers in C involves basic programming concepts such as variable declaration, user input, arithmetic operations, and output display. By understanding the foundational elements of C, including data types, loops, and functions, programmers can efficiently perform such tasks and build a strong basis for more complex programming endeavors.

Remember that programming is not just about solving specific problems; it’s about learning to think logically and breaking down problems into smaller, manageable tasks. The ability to calculate averages in C is just one step on the journey to becoming a proficient programmer.

Leave a Comment