---
name: "cbrt"
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/cbrt"
---

# cbrt(3)

cube root function

## NAME

cbrt, cbrtf, cbrtl - cube root function

## LIBRARY

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

## SYNOPSIS

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

**double cbrt(double** *x***);** **float cbrtf(float** *x***);** **long double cbrtl(long double** *x***);**

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

**cbrt**():

```
    _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
        || _XOPEN_SOURCE >= 500
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

**cbrtf**(), **cbrtl**():

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

## DESCRIPTION

These functions return the (real) cube root of *x*. This function cannot fail; every representable real value has a real cube root, and rounding it to a representable value never causes overflow nor underflow.

## RETURN VALUE

These functions return the cube root of *x*.

If *x* is +0, -0, positive infinity, negative infinity, or NaN, *x* 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** |
| **cbrt**(), **cbrtf**(), **cbrtl**() | Thread safety | MT-Safe |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

GNU, C99, POSIX.1-2001.

## SEE ALSO

[**pow**(3)](/pow/3.md), [**sqrt**(3)](/sqrt/3.md)