Herewith the part of the Weights And Measures Act (1985) (as amended) that tells you the only two remaining things (as of almost 17 years ago) that can be sold in pints:
Yes? I don't mean to say it's not exact. I'm just saying that when people order pints of beer, they're not thinking about exactly how much liquid that is, that's just what you order.
Exactly. "Pint" and "half" are the local version of "large" and "small".
Bottled beer volumes can vary between 568mL (UK produced), whatever an American pint is for American exports, and 330mL (small bottles), 500mL (large bottles), and 750mL (huge bottles). The metric sizes are common for British produces, as well as the rest of the world -- presumably, standard sized glass bottles are cheaper.