C++ programs to calculate compound interest have been shown here. Both of the iterative and recursive approaches have been covered. Computing compound interest using formula has also been shown here.

The following section covers the C++ programs to calculate compound interest.

## 1. C++ Program & output to calculate compound interest using formula

Code has been copied
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alphabetacoder.com
C++ program to calculate compound interest using formula
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#include <iostream>
#include <cmath>

using namespace std;

int main(){
// declare variables
float ci, amount, p, r, t;
int n;

// take input of initial principal amount,
// interest rate, periodicity of payment and year
cout<<"Enter the principal balance = ";
cin>> p;
cout<<"Enter the annual interest rate = ";
cin>> r;
cout<<"Enter compound frequency / year = ";
cin>> n;
cout<<"Enter the year  = ";
cin>> t;

// calculate compounded value
// using formula
amount = p * pow((1 + r/(100 * n)), n*t);

//find the compound interest
ci = amount - p;

// display result
cout<<"Compound interest = "<<ci<<endl;

return 0;
}


Output

Enter the principal balance = 17000

Enter the annual interest rate = 10

Enter compound frequency / year = 1

Enter the year = 2

Compound interest = 3570

## 2. C++ Program & output to calculate compound interest using loop (Iteration)

Code has been copied
/***************************************************************
alphabetacoder.com
C++ program to calculate compound interest using loop (Iteration)
****************************************************************/

#include <iostream>

using namespace std;

int main(){
// declare variables
float ci, amount, p, r, t;
int n, i;

// take input of initial principal amount,
// interest rate, compound frequency and year
cout<<"Enter the principal balance = ";
cin>> p;
cout<<"Enter the annual interest rate = ";
cin>> r;
cout<<"Enter compound frequency / year = ";
cin>> n;
cout<<"Enter the year  = ";
cin>> t;

// initialize
amount = p;

// calculate compounded value using loop
for(i = 0; i < n * t; i++)
amount = amount + amount * (r / (n * 100));

//find the compound interest
ci = amount - p;

// display result
cout<<"Compound interest = "<<ci<<endl;

return 0;
}


Output

Enter the principal balance = 5000

Enter the annual interest rate = 7.5

Enter compound frequency / year = 4

Enter the year = 6

Compound interest = 2808.96

## 3. C++ Program & output to calculate compound interest using recursion

Code has been copied
/***************************************************************
alphabetacoder.com
C++ program to calculate compound interest using recursion
****************************************************************/

#include <iostream>

using namespace std;

// recursive function to compute compound interest
float compound_interest(float p0, float p, float r, int n, int t, int itr){
// if number of total no of compound reached
if(itr == n * t)
return (p - p0);
// calculate interest
float interest = p * (r / (n * 100));

// call function
return compound_interest(p0, p + interest, r, n, t, itr + 1);
}

int main(){
// declare variables
float ci, p, r;
int n, t;

// take input of initial principal amount,
// interest rate, compound frequency and year
cout<<"Enter the principal balance = ";
cin>> p;
cout<<"Enter the annual interest rate = ";
cin>> r;
cout<<"Enter compound frequency / year = ";
cin>> n;
cout<<"Enter the year  = ";
cin>> t;

// call function to compute compound interest
ci = compound_interest(p, p, r, n, t, 0);

// display result
cout<<"Compound interest = "<<ci<<endl;

return 0;
}


Output

Enter the principal balance = 2700

Enter the annual interest rate = 5

Enter compound frequency / year = 4

Enter the year = 10

Compound interest = 1737.77