lround man page

lround, lroundf, lroundl, llround, llroundf, llroundl — round to nearest integer, away from zero


#include <math.h>

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

long long int llround(double x);
long long int llroundf(float x);
long long int llroundl(long double x);

Link with -lm.

Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

All functions shown above:



These functions round their argument to the nearest integer value, rounding away from zero, regardless of the current rounding direction (see fenv(3)).

Note that unlike the round(3) and ceil(3), functions, the return type of these functions differs from that of their arguments.

Return Value

These functions return the rounded integer value.

If x is a NaN or an infinity, or the rounded value is too large to be stored in a long (long long in the case of the ll* functions), then a domain error occurs, and the return value is unspecified.


See math_error(7) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

Domain error: x is a NaN or infinite, or the rounded value is too large

An invalid floating-point exception (FE_INVALID) is raised.

These functions do not set errno.


These functions first appeared in glibc in version 2.1.


For an explanation of the terms used in this section, see attributes(7).

Interface Attribute Value
lround(), lroundf(), lroundl(),
llround(), llroundf(), llroundl()
Thread safety MT-Safe

Conforming to

C99, POSIX.1-2001, POSIX.1-2008.

See Also

ceil(3), floor(3), lrint(3), nearbyint(3), rint(3), round(3)


This page is part of release 4.10 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at

Referenced By

lrint(3), round(3).

llround(3), llroundf(3), llroundl(3), lroundf(3) and lroundl(3) are aliases of lround(3).

2016-03-15 Linux Programmer's Manual