Nomenclature for per $2^n$?

Question

We have the nomenclature percent to describe a number of something per hundred units:

Example: 1/2 = 50% (percent)

I wonder if there is a nomenclature for per $2^n$ units? Like there are binary prefixes for counting bytes (KiB, MiB, ...).

Example: 1/2 = 128 per 256 (?)