A dollar can be divided up into 100 cents.
A Swiss franc can be divided into 100 rappen.
What are the words that describe these units (dollar vs cents or franc vs rappen)? I found out that currencies that are based on the decimal system are called "decimalised" currencies. But I did not find a word to describe the "base unit" and the "sub unit" for arbitrary currencies.
Usage example: "This number describes <x>, but it needs to be converted to <y>".
Best Answer
The smaller currency unit or value, in countries that have one, is generically called a fractional monetary unit:
The link from Free Dictionary gives both the definition and several examples (like cent, centavo, fil, piaster). The definition also suggests that the basic unit is called just that, the basic monetary unit.
In your example, I would write:
If you've already established you are talking about money, you can drop the "monetary," otherwise leave it as is.