C++ round()

The round() function in C++ returns the integral value that is nearest to the argument, with halfway cases rounded away from zero.

round() prototype [As of C++ 11 standard]

double round(double x);
float round(float x);
long double round(long double x);
double round(T x); // For integral type

The round() function takes a single argument and returns a value of type double, float or long double type. This function is defined in <cmath> header file.

round() Parameters

The round() function takes a single argument value to round.

round() Return value

The round() function returns the integral value that is nearest to x, with halfway cases rounded away from zero.

Example 1: How round() works in C++?

#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    double x = 11.16, result;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;

    x = 13.87;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;
    
    x = 50.5;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;
    
    x = -11.16;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;

    x = -13.87;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;
    
    x = -50.5;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;
    
    return 0;
}

When you run the program, the output will be:

round(11.16) = 11
round(13.87) = 14
round(50.5) = 51
round(-11.16) = -11
round(-13.87) = -14
round(-50.5) = -51

Example 2: round() function for integral types

#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    int x = 15;
    double result;
    result = round(x);
    cout << "round(" << x << ") = " << result << endl;

    return 0;
}

When you run the program, the output will be:

round(15) = 15

For integral values, applying the round function returns the same value as the input. So it is not commonly used for integral values in practice.