The cuntmeter is used because of complete lack of interest in converting units, and/or the resulting answer. Problems most likely to use cuntmeters typically come from textbook questions, but can be used in any aspect of life. The product doesn't really matter, because if it did, the corresponding units would have been calculated from the beginning.
If in fact the answer DID matter, the person recording the measurements would have to really be a big greasy cunt to record them all in different units. Even if the measurements came from different sources, they should have been converted into a standard unit. Thus, the cuntmeter is born.