cbrt, cbrtf, cbrtl

Defined in header <math.h>
float       cbrtf( float arg );
(1) (since C99)
double      cbrt( double arg );
(2) (since C99)
long double cbrtl( long double arg );
(3) (since C99)
Defined in header <tgmath.h>
#define cbrt( arg )
(4) (since C99)
1-3) Computes the cubic root of arg.
4) Type-generic macro: If arg has type long double, cbrtl is called. Otherwise, if arg has integer type or the type double, cbrt is called. Otherwise, cbrtf is called.


arg - floating point value

Return value

If no errors occur, the cubic root of arg (3arg), is returned.

If a range error occurs due to underflow, the correct result (after rounding) is returned.

Error handling

Errors are reported as specified in math_errhandling.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

  • if the argument is ±0 or ±∞, it is returned, unchanged
  • if the argument is NaN, NaN is returned.


cbrt(arg) is not equivalent to pow(arg, 1.0/3) because pow cannot raise a negative base to a fractional exponent.


#include <stdio.h>
#include <math.h>
int main(void)
    // normal use
    printf("cbrt(729) = %f\n", cbrt(729));
    printf("cbrt(-0.125) = %f\n", cbrt(-0.125));
    // special values
    printf("cbrt(-0) = %f\n", cbrt(-0.0));
    printf("cbrt(+inf) = %f\n", cbrt(INFINITY));


cbrt(729) = 9.000000
cbrt(-0.125) = -0.500000
cbrt(-0) = -0.000000
cbrt(+inf) = inf


  • C11 standard (ISO/IEC 9899:2011):
    • The cbrt functions (p: 247)
    • 7.25 Type-generic math <tgmath.h> (p: 373-375)
    • F.10.4.1 The cbrt functions (p: 524)
  • C99 standard (ISO/IEC 9899:1999):
    • The cbrt functions (p: 228)
    • 7.22 Type-generic math <tgmath.h> (p: 335-337)
    • F.9.4.1 The cbrt functions (p: 460)

See also

computes a number raised to the given power (xy)
computes square root (x)
computes square root of the sum of the squares of two given numbers (x2

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