C++ Program to Calculate the Simple Interest

In this tutorial, we will learn about Simple Interest in C++ i.e. how to write a program to calculate the simple interest using C++.

Quick Info:💡

↪ As we know, Simple Interest(S.I) is a quick and easy method of calculating the interest charge on a loan.

↪ For calculating the Simple interest, we require parameters like principal(P), rate(R) and time(T). The formula for calculating Simple Interest is (P*R*T)/100.

↪ Here’s the following steps to calculate the Simple Interest:

  • First, initialize the variables- principal, rate, time and SI.
  • Second, find the Simple interest using formula.
  • Third, print the result of SI on the output console.

Code to calculate simple interest can be performed in two ways:

Program to Calculate Simple Interest Using Direct Method

Here’s a direct method to calculate Simple Interest.

Simply, the user will be asked to enter the values then, the result is computed according to code provided and then displayed to a user.


void main()
int simple_interest,principal,rate,time;
cout<<"Enter principal";
cout<<"Enter rate";
cout<<"Enter time";
cout<<"Simple Interest is:="<<simple_interest;
Enter principal 12000
Enter rate 2
Enter time 2
Simple Interest is:=480


Flow of the program internally:


Program to Calculate Simple Interest Using Function

Functions are used to perform certain actions, and they are important for reusing code: Define the code once and use it many times.

And, this is a another method to calculate Simple Interest at large amount i.e. by function.

Note: Always remember that execution starts from the main body only.


double SI(double principal, double rate, double time)
double simple_interest;
return simple_interest;
double main(){
double SI1=SI(12000,2,2);
double SI2=SI(5500,2,3.5);
cout<<"Simple Interest for SI1 is:="<<SI1<<endl;
cout<<"Simple Interest for SI2 is:="<<SI2<<endl;
return 0;
Simple Interest for SI1 is:=480
Simple Interest for SI2 is:=385


Flow of a program:

Well, I hope it really helped you to know the C++ better.

Attention reader⚠ Don’t stop learning now.

Just stay with us to get more such exciting codes to explore more in C++.

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