---
name: "scalb"
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/scalb"
---

# scalb(3)

scale by an integer power of radix (OBSOLETE)

## NAME

scalb, scalbf, scalbl - scale by an integer power of radix (OBSOLETE)

## LIBRARY

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

## SYNOPSIS

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

**\[\[deprecated\]\] double scalb(double** *x***, double** *e***);** **\[\[deprecated\]\] float scalbf(float** *x***, float** *e***);** **\[\[deprecated\]\] long double scalbl(long double** *x***, long double** *e***);**

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

**scalb**():

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

**scalbf**(), **scalbl**():

```
    _XOPEN_SOURCE >= 600
        || /* Since glibc 2.19: */ _DEFAULT_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

These functions multiply their first argument *x* by **FLT\_RADIX** (probably 2) to the power of *e*, that is:

```
    x * FLT_RADIX ** e
```

The definition of **FLT\_RADIX** can be obtained by including *\<float.h\>*.

## RETURN VALUE

On success, these functions return *x* \* **FLT\_RADIX** \*\* *e*.

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

If *x* is positive infinity (negative infinity), and *e* is not negative infinity, positive infinity (negative infinity) is returned.

If *x* is +0 (-0), and *e* is not positive infinity, +0 (-0) is returned.

If *x* is zero, and *e* is positive infinity, a domain error occurs, and a NaN is returned.

If *x* is an infinity, and *e* is negative infinity, a domain error occurs, and a NaN is returned.

If the result overflows, a range error occurs, and the functions return **HUGE\_VAL**, **HUGE\_VALF**, or **HUGE\_VALL**, respectively, with a sign the same as *x*.

If the result underflows, a range error occurs, and the functions return zero, with a sign the same as *x*.

## 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 0, and *e* is positive infinity, or *x* is positive infinity and *e* is negative infinity and the other argument is not a NaN

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

- Range error, overflow

  *errno* is set to **ERANGE**. An overflow floating-point exception (**FE\_OVERFLOW**) is raised.

- Range error, underflow

  *errno* is set to **ERANGE**. An underflow floating-point exception (**FE\_UNDERFLOW**) is raised.

## ATTRIBUTES

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

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **scalb**(), **scalbf**(), **scalbl**() | Thread safety | MT-Safe |

## STANDARDS

None.

## HISTORY

- **scalb**()

  4\.3BSD. Obsolescent in POSIX.1-2001; Removed in POSIX.1-2008, recommending the use of [**scalbln**(3)](/scalbln/3.md), [**scalblnf**(3)](/scalblnf/3.md), or [**scalblnl**(3)](/scalblnl/3.md) instead.

## BUGS

Before glibc 2.20, these functions did not set *errno* for domain and range errors.

## SEE ALSO

[**ldexp**(3)](/ldexp/3.md), [**scalbln**(3)](/scalbln/3.md)