fabs, fabsf, fabsl

Calculates the absolute value of the floating-point argument.


double fabs(
   double x
float fabs(
   float x
); // C++ only
long double fabs(
   long double x
); // C++ only
float fabsf(
   float x
long double fabsl(
   long double x

#define fabs(X) // Requires C11 or higher


Floating-point value.

Return value

The fabs functions return the absolute value of the argument x. There's no error return.

Input SEH exception _matherr exception
± QNaN, IND none _DOMAIN


C++ allows overloading, so you can call overloads of fabs if you include the <cmath> header. In a C program, unless you're using the <tgmath.h> macro to call this function, fabs always takes and returns a double.

If you use the fabs macro from <tgmath.h>, the type of the argument determines which version of the function is selected. See Type-generic math for details.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.


Function Required C header Required C++ header
fabs, fabsf, fabsl <math.h> <cmath> or <math.h>
fabs macro <tgmath.h>

For more compatibility information, see Compatibility.


See the example for abs.

See also

Math and floating-point support
abs, labs, llabs, _abs64