In this C++ tutorial, you will learn how to round given number to nearest integral value using nearbyint() function of cmath, with syntax and examples.

C++ nearbyint()

C++ nearbyint(x) rounds argument x to nearest integral value, using current rounding mode.

The current rounding mode can be accessed using fesetround() and fegetround().


The syntax of C++ nearbyint() is



xA double, float, long double, or integral type value.


The return value depends on the type of value passed for parameter x.

The return value of nearbyint(x) is

  • double if x is double or integral type.
  • float if x is float.
  • long double if x is long double.

The synopsis of nearbyint() function is

double sinh(double x);
float sinh(float x);
long double sinh(long double x);
double sinh(T x); // for integral type argument values

nearbyint() is a function of cmath library. Include cmath library at the start of program, if using nearbyint() function.



In this example, we read a value from user into variable x, and find the nearest integral value of x using nearbyint() function.

C++ Program

#include <iostream>
using namespace std;

int main() {
    double x;
    cout << "Enter x   : ";
    cin >> x;
    double result = nearbyint(x);
    cout << "nearbyint(" << x << ") : " << result << endl;


Enter x   : 5.23
nearbyint(5.23) : 5
Program ended with exit code: 0
Enter x   : 9.89
nearbyint(9.89) : 10
Program ended with exit code: 0
Enter x   : nan
nearbyint(nan) : nan
Program ended with exit code: 0


In this C++ Tutorial, we learned the syntax of C++ nearbyint(), and how to use this function to find the nearest integral value, with the help of examples.