---
name: "erf"
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/erf"
---

# erf(3)

error function operators

## NAME

**erf**, **erff**, **erfl**, **erfc**, **erfcf**, **erfcl** – error function operators

## LIBRARY

Math Library (libm, -lm)

## SYNOPSIS

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

*double*\

**erf**(*double x*);

*float*\

**erff**(*float x*);

*long double*\

**erfl**(*long double x*);

*double*\

**erfc**(*double x*);

*float*\

**erfcf**(*float x*);

*long double*\

**erfcl**(*long double x*);

## DESCRIPTION

These functions calculate the error function of *x*.

The **erf**(), **erff**(), and **erfl**() functions calculate the error function of x; where

erf(x) = 2/sqrt(pi)∗integral from 0 to x of exp(-t∗t) dt.

The **erfc**(), **erfcf**(), and **erfcl**() functions calculate the complementary error function of *x*; that is **erfc**() subtracts the result of the error function **erf**(*x*) from 1.0.

## SEE ALSO

[math(3)](/math/3.md)

## STANDARDS

The **erf**(), **erff**(), **erfl**(), **erfc**(), **erfcf**() and **erfcl**() functions conform to ISO/IEC 9899:1999 (“ISO C99”).

## HISTORY

The **erf**() and **erfc**() functions appeared in 4.3BSD.