array vector spare size

Hi list,

does anybody have a good understanding of how much memory can be expected to be wasted at worst in the array vector of tables?

The X in something like: | unused pre-allocated memory = log2(entries) * X byte | so that an estimation could be made from this that the cost of overhead memory for one entry is between | log2(entries) * Xbest byte and log2(entries) * Xworse byte| ?

The log2() might be wrong, it might be sth. else instead.

Thanks in advance,
Henning