fmod() function in C++ and its uses

In this section, we will learn the concept of fmod() function and understand its implementation with an example.

fmod() function in C++

  • In C++ there are various types of inbuilt function which helps us to perform a mathematical operation on floating-point numbers.
  • The fmod() function is one of those inbuilt functions in the <cmath> header file which is used to return the remainder or the modulus of two floating-point numbers. It accepts 2 numbers as numerator and denominator and calculates the reminder rounded towards zero.
  • The function returns the value of type double which is the floating-point modulus of the division.


double fmod(double a, double b);

//Where a = Numerator and b = Denominator

//The function returns the reminder of dividing a/b.

Note: To perform a valid operation using fmod() function, the denominator value should always be greater than 0, otherwise it will return a null value.

Example program for fmod() function

Let’s understand the use of fmod() with an example:

#include <iostream>
#include <cmath>
using namespace std;

int main()
    double a,b,reminder;
    //Input the value of numerator and denominator
    cout << "Enter the numerator value:" << endl;
    cin >> a;
    cout << "Enter the denominator value:" << endl;
    cin >> b;
    reminder = fmod(a, b); //function call
    cout << "Remainder of " << a << "/" << b << " = " << reminder << endl;
    //Let's take the denominator 0
    b = 0;
    reminder = fmod(a, b); //function call
    cout << "Remainder of " << a << "/" << b << " = " << reminder << endl;

    return 0;


Enter the numerator value:
Enter the denominator value:
Remainder of 7.8/9.4 = 7.8
Remainder of 7.8/0 = -nan

Hope this article has helped you to understand the fmod( ) function and its uses in C++.

Happy Coding!!!

You can also read, Mathematical functions in C++

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