---
name: "fmax"
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/fmax"
---

# fmax(3)

determine maximum of two floating-point numbers

## NAME

fmax, fmaxf, fmaxl - determine maximum of two floating-point numbers

## LIBRARY

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

## SYNOPSIS

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

**double fmax(double** *x***, double** *y***);** **float fmaxf(float** *x***, float** *y***);** **long double fmaxl(long double** *x***, long double** *y***);**

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

**fmax**(), **fmaxf**(), **fmaxl**():

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

## DESCRIPTION

These functions return the larger value of *x* and *y*.

## RETURN VALUE

These functions return the maximum of *x* and *y*.

If one argument is a NaN, the other argument is returned.

If both arguments are NaN, a NaN 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** |
| **fmax**(), **fmaxf**(), **fmaxl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

glibc 2.1. C99, POSIX.1-2001.

## SEE ALSO

[**fdim**(3)](/fdim/3.md), [**fmin**(3)](/fmin/3.md)