C Programming Code Examples C > Beginners Lab Assignments Code Examples C program to calculate Simple Interest C program to calculate Simple Interest Write a C program to input principle, time and rate (P, T, R) from user and find Simple Interest. How to calculate simple interest in C programming. Logic to find simple interest in C program. Input principle amount in some variable say principle. Input time in some variable say time. Input rate in some variable say rate. Find simple interest using formula SI = (principle * time * rate) / 100. Finally, print the resultant value of SI. #include <stdio.h> int main() { float principle, time, rate, SI; /* Input principle, rate and time */ printf("Enter principle (amount): "); scanf("%f", &principle); printf("Enter time: "); scanf("%f", &time); printf("Enter rate: "); scanf("%f", &rate); /* Calculate simple interest */ SI = (principle * time * rate) / 100; /* Print the resultant value of SI */ printf("Simple Interest = %f", SI); return 0; }