There are certainly other factors, but a cup is far from the specific solution you seek [0]. There's only one country that has current unit definition of a cup (the US), which is 8 (US) fluid ounces (fl.oz) (or 236.6ml), or differently as a "legal" cup at 240ml [1]. It used to be defined as 10 Imperial fl.oz in the UK (284ml), although rarely used. While much of the world defines a metric cup as 250ml. But then there's the exception that is coffee.. a cup of coffee in the US is the product of using 5 fl.oz producing approximately 4 fl.oz of coffee[0]

A "cup": 118-284ml

[0]: https://en.wikipedia.org/wiki/Cup_%28unit%29 [1]: https://www.fda.gov/regulatory-information/search-fda-guidan...