---
name: "fabs"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/fabs"
---

# fabs(3)

floating-point absolute value functions

## NAME

**fabs**, **fabsf**, **fabsl** – floating-point absolute value functions

## LIBRARY

Math Library (libm, -lm)

## SYNOPSIS

**#include \<math.h\>**

*double*\

**fabs**(*double x*);

*float*\

**fabsf**(*float x*);

*long* *double*\

**fabsl**(*long double x*);

## DESCRIPTION

The **fabs**(), **fabsf**() and **fabsl**() functions compute the absolute value of a floating-point number *x*.

## RETURN VALUES

The **fabs**(), **fabsf**() and **fabsl**() functions return the absolute value of *x*.

## SEE ALSO

[abs(3)](/abs/3.md), [ceil(3)](/ceil/3.md), [floor(3)](/floor/3.md), [ieee(3)](/ieee/3.md), [math(3)](/math/3.md), [rint(3)](/rint/3.md)

## STANDARDS

The **fabs**() function conforms to ISO/IEC 9899:1990 (“ISO C90”). The **fabsf**() and **fabsl**() functions conform to ISO/IEC 9899:1999 (“ISO C99”).