---
name: "floorl"
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/floor"
---

# floorl(3)

largest integral value not greater than argument

Part of [floor(3)](/floor/3.md).

## NAME

floor, floorf, floorl - largest integral value not greater than argument

## LIBRARY

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

## SYNOPSIS

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

**double floor(double** *x***);** **float floorf(float** *x***);** **long double floorl(long double** *x***);**

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

**floorf**(), **floorl**():

```
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

These functions return the largest integral value that is not greater than *x*.

For example, *floor(0.5)* is 0.0, and *floor(-0.5)* is -1.0.

## RETURN VALUE

These functions return the floor of *x*.

If *x* is integral, +0, -0, NaN, or an infinity, *x* itself is returned.

## ERRORS

No errors occur.

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **floor**(), **floorf**(), **floorl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

C99, POSIX.1-2001.

The variant returning *double* also conforms to SVr4, 4.3BSD, C89.

SUSv2 and POSIX.1-2001 contain text about overflow (which might set *errno* to **ERANGE**, or raise an **FE\_OVERFLOW** exception). In practice, the result cannot overflow on any current machine, so this error-handling stuff was just nonsense. (More precisely, overflow can happen only when the maximum value of the exponent is smaller than the number of mantissa bits. For the IEEE-754 standard 32-bit and 64-bit floating-point numbers the maximum value of the exponent is 127 (respectively, 1023), and the number of mantissa bits including the implicit bit is 24 (respectively, 53).) This was removed in POSIX.1-2008.

## SEE ALSO

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