Calculate interest amount by using formula in C language

In C programming, calculating interest on deposited amounts is a common financial calculation. This program demonstrates how to compute the final amount after applying continuous compound interest over a specified period.

Syntax

A = P * exp((r/100) * t)

Where:

• P = Principal amount (initial deposit)
• r = Annual interest rate (percentage)
• t = Time period in years
• A = Final amount after interest

Algorithm

START
Step 1: Declare double variables P, r, t, A, M
Step 2: Read principal amount to be deposited
Step 3: Read annual interest rate
Step 4: Read number of years for deposit
Step 5: Calculate final amount using continuous compound interest
        I.  M = (r/100) * t
        II. A = P * exp(M)
Step 6: Display the final amount
STOP

Example

The following program calculates the amount after applying continuous compound interest −

#include <stdio.h>
#include <math.h>

int main() {
    double P, r, t, A, M;
    
    printf("Amount to be deposited in the bank: ");
    scanf("%lf", &P);
    
    printf("Enter the rate of interest: ");
    scanf("%lf", &r);
    
    printf("How many years you want to deposit: ");
    scanf("%lf", &t);
    
    /* Calculate using continuous compound interest formula */
    M = (r/100) * t;
    A = P * exp(M);
    
    printf("Amount after %.1lf years with interest is: %.2lf<br>", t, A);
    
    return 0;
}

Output

Amount to be deposited in the bank: 50000
Enter the rate of interest: 6.5
How many years you want to deposit: 5
Amount after 5.0 years with interest is: 69201.53

Key Points

• This program uses the continuous compound interest formula with the exponential function exp().
• The math.h header is required for the exp() function.
• All variables are declared as double for precise financial calculations.

Conclusion

This C program efficiently calculates compound interest using the exponential function. The continuous compounding formula provides accurate results for financial planning and investment calculations.