Base64: What is the worst possible increase in space usage?

16kb is 131,072 bits. Base64 packs 24-bit buffers into four 6-bit characters apiece, so you would have 5,462 * 4 = 21,848 bytes.

From Wikipedia

Note that given an input of n bytes, the output will be (n + 2 - ((n + 2) % 3)) / 3 * 4 bytes long, so that the number of output bytes per input byte converges to 4 / 3 or 1.33333 for large n.

So 16kb * 4 / 3 gives very little over 21.3' kb, or 21848 bytes, to be exact.

Hope this helps

Base64 encodes each set of three bytes into four bytes. In addition the output is padded to always be a multiple of four.

This means that the size of the base-64 representation of a string of size n is:

ceil(n / 3) * 4

So, for a 16kB array, the base-64 representation will be ceil(16*1024/3)*4 = 21848 bytes long ~= 21.8kB.

A rough approximation would be that the size of the data is increased to 4/3 of the original.