---
name: "remainder"
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/remainder"
---

# remainder(3)

floating-point remainder function

## NAME

drem, dremf, dreml, remainder, remainderf, remainderl - floating-point remainder function

## LIBRARY

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

## SYNOPSIS

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

**double remainder(double** *x***, double** *y***);** **float remainderf(float** *x***, float** *y***);** **long double remainderl(long double** *x***, long double** *y***);**

/\* Obsolete synonyms \*/ **\[\[deprecated\]\] double drem(double** *x***, double** *y***);** **\[\[deprecated\]\] float dremf(float** *x***, float** *y***);** **\[\[deprecated\]\] long double dreml(long double** *x***, long double** *y***);**

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

**remainder**():

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

**remainderf**(), **remainderl**():

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

**drem**(), **dremf**(), **dreml**():

```
    /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

These functions compute the remainder of dividing *x* by *y*. The return value is *x-n\*y*, where *n* is the value *x / y*, rounded to the nearest integer. If the absolute value of *x-n\*y* is 0.5, *n* is chosen to be even.

These functions are unaffected by the current rounding mode (see [**fenv**(3)](/fenv/3.md)).

The **drem**() function does precisely the same thing.

## RETURN VALUE

On success, these functions return the floating-point remainder, *x-n\*y*. If the return value is 0, it has the sign of *x*.

If *x* or *y* is a NaN, a NaN is returned.

If *x* is an infinity, and *y* is not a NaN, a domain error occurs, and a NaN is returned.

If *y* is zero, and *x* is not a NaN, a domain error occurs, and a NaN is returned.

## ERRORS

See [**math\_error**(7)](/math_error/7.md) for information on how to determine whether an error has occurred when calling these functions.

The following errors can occur:

- Domain error: *x* is an infinity and *y* is not a NaN

  *errno* is set to **EDOM** (but see BUGS). An invalid floating-point exception (**FE\_INVALID**) is raised.

-

  These functions do not set *errno* for this case.

- Domain error: *y* is zero

  *errno* is set to **EDOM**. An invalid floating-point exception (**FE\_INVALID**) is raised.

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **drem**(), **dremf**(), **dreml**(), **remainder**(), **remainderf**(), **remainderl**() | Thread safety | MT-Safe |

## STANDARDS

- **remainder**() **remainderf**() **remainderl**()

  C11, POSIX.1-2008.

- **drem**() **dremf**() **dreml**()

  None.

## HISTORY

- **remainder**() **remainderf**() **remainderl**()

  C99, POSIX.1-2001.

- **drem**()

  4\.3BSD.

- **dremf**() **dreml**()

  Tru64, glibc2.

## BUGS

Before glibc 2.15, the call

```
remainder(nan(""), 0);
```

returned a NaN, as expected, but wrongly caused a domain error. Since glibc 2.15, a silent NaN (i.e., no domain error) is returned.

Before glibc 2.15, *errno* was not set to **EDOM** for the domain error that occurs when *x* is an infinity and *y* is not a NaN.

## EXAMPLES

The call "remainder(29.0, 3.0)" returns -1.

## SEE ALSO

[**div**(3)](/div/3.md), [**fmod**(3)](/fmod/3.md), [**remquo**(3)](/remquo/3.md)