How old have you got to be to go to a nightclub in the UK?

It depends on where. In the US, the legal drinking age is 21, and most states have strict requirements for bars/clubs about when they are able to allow people under 21 in. For example, some states allow clubs to admit people who are 18 and over, but only if wristbands or other identification is required for drinks. Often, bars and clubs find it difficult and expensive (insurance) to allow under 21 patrons, and therefore set the age limit at 21.

Therefore, the majority of clubs in the US are 21+, but some are 18+, or even younger. Some also have certain "college nights" where they allow younger patrons.