---
name: "atof"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/atof/3"
---

# atof(3)

convert a string to a double

## NAME

atof - convert a string to a double

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <stdlib.h>
```

**double atof(const char \****nptr***);**

## DESCRIPTION

The **atof**() function converts the initial portion of the string pointed to by *nptr* to *double*. The behavior is the same as

```
strtod(nptr, NULL);
```

except that **atof**() does not detect errors.

## RETURN VALUE

The converted value.

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **atof**() | Thread safety | MT-Safe locale |

## STANDARDS

C11, POSIX.1-2008.

## HISTORY

POSIX.1-2001, C89, C99, SVr4, 4.3BSD.

## SEE ALSO

[**atoi**(3)](/atoi/3.md), [**atol**(3)](/atol/3.md), [**strfromd**(3)](/strfromd/3.md), [**strtod**(3)](/strtod/3.md), [**strtol**(3)](/strtol/3.md), [**strtoul**(3)](/strtoul/3.md)