roundup - Man Page

round up in steps


Standard C library (libc)


#include <sys/param.h>

roundup(x, step);


This macro rounds x to the nearest multiple of step that is not less than x.

It is typically used for rounding up a pointer to align it or increasing a buffer to be allocated.

This API is not designed to be generic, and doesn't work in some cases that are not important for the typical use cases described above. See Caveats.

Return Value

This macro returns the rounded value.


This nonstandard macro is present in glibc and some BSDs.


The arguments may be evaluated more than once.

x should be nonnegative, and step should be positive.

If x + step would overflow or wrap around, the behavior is undefined.

See Also

ceil(3), floor(3), lrint(3), rint(3), lround(3), round(3)


2023-01-19 Linux man-pages 6.03