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

C++ lround()

C++ lround() returns the long int value nearest to the given value.


The syntax of C++ lround() is



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


The function returns value of type long int.

The synopsis of lround() function is

long int lround(float x);
long int lround(double x);
long int lround(long double x);

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



In this example, we read a double value from user into variable x, and find the nearest long integer to this value in x, using round().

C++ Program

#include <iostream>
using namespace std;

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


Enter a number : 1.96233699998745455
lround(1.96234) : 2
Program ended with exit code: 0
Enter a number : -1.24210
lround(-1.2421) : -1
Program ended with exit code: 0


In this C++ Tutorial, we learned the syntax of C++ lround(), and how to use this function to round the given value to nearest long int, with the help of examples.