C program to calculate compound interest

In this post, you will learn how to calculate the compound interest using the C programming language.

Compound interest is the addition of interest to the principal sum of a loan or deposit, or in other words, interest on interest. Compound interest makes a sum of money grow at a faster rate than simple interest because in addition to earning returns on the money you invest, you also earn returns on those returns at the end of every compounding period.

Compound Interest Formula

The Compound Interest (C.I.) formula is calculated as -

Compound Interest = P(1 + R/100)r 

Where,
P is the principle amount
T is the time and
R is the rate

C program to calculate Compound Interest

In the given C program, we allow users to enter the principal amount, rate of interest, and number of years. By using these values, the program calculates compound interest.

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

int main()
{
    float p, r, t, CI;

    // Input principle, time and rate
    printf("Enter the principal amount : ");
    scanf("%f", &p);

    printf("Enter the time span : ");
    scanf("%f", &t);

    printf("Enter rate of interest : ");
    scanf("%f", &r);

    // Calculate compound interest
    CI = p* (pow((1 + r / 100), t));

    printf("Compound Interest = %f", CI);

    return 0;
}

Enter the principal amount : 34000
Enter the time span : 5
Enter rate of interest : 6.5
Compound Interest = 46582.960938

Enter the principal amount : 42000
Enter the time span : 8
Enter rate of interest : 7.5
Compound Interest = 74906.093750

C program to calculate Compound Interest using function

In the given C program, we define a user function to calculate the compound interest.

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

float compound_interest(float P, float T, float R) {
   return P*(pow(1+(R/100), T));
}
int main() {
   float p, t, r;
   printf("Enter Principle amount, rate of interest, and time: ");
   scanf("%f%f%f", &p, &r, &t);
   printf("Interest value: %f", compound_interest(p, t, r));
}

Enter Principle amount, rate of interest, and time: 12000 4.7 5
Interest value: 15097.837891

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