---
name: "clog2"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/clog2"
---

# clog2(3)

base-2 logarithm of a complex number

## NAME

clog2, clog2f, clog2l - base-2 logarithm of a complex number

## LIBRARY

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

## SYNOPSIS

```
#include <complex.h>
```

**double complex clog2(double complex** *z***);** **float complex clog2f(float complex** *z***);** **long double complex clog2l(long double complex** *z***);**

## DESCRIPTION

The call *clog2(z)* is equivalent to *clog(z)/log(2)*.

The other functions perform the same task for *float* and *long double*.

Note that *z* close to zero will cause an overflow.

## STANDARDS

None.

## HISTORY

These function names are reserved for future use in C99.

Not yet in glibc, as at glibc 2.19.

## SEE ALSO

[**cabs**(3)](/cabs/3.md), [**cexp**(3)](/cexp/3.md), [**clog**(3)](/clog/3.md), [**clog10**(3)](/clog10/3.md), [**complex**(7)](/complex/7.md)