---
name: "lround"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/lround"
---

# lround(3)

round to nearest integer

## NAME

lround, lroundf, lroundl, llround, llroundf, llroundl - round to nearest integer

## LIBRARY

Math library (*libm*, *-lm*)

## SYNOPSIS

```
#include <math.h>
```

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

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

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

All functions shown above:

```
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
```

## DESCRIPTION

These functions round their argument to the nearest integer value, rounding halfway cases away from zero, regardless of the current rounding direction (see [**fenv**(3)](/fenv/3.md)).

Note that unlike the [**round**(3)](/round/3.md) and [**ceil**(3)](/ceil/3.md), 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.

## ERRORS

See [**math\_error**(7)](/math_error/7.md) 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*.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

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

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## SEE ALSO

[**ceil**(3)](/ceil/3.md), [**floor**(3)](/floor/3.md), [**lrint**(3)](/lrint/3.md), [**nearbyint**(3)](/nearbyint/3.md), [**rint**(3)](/rint/3.md), [**round**(3)](/round/3.md)