I usually start getting what I term 'the buzz' (when I start to actually feel something) by the third or fourth pint of it, depending on the cider in question. So I guess I'd count as 'tipsy' by maybe the 5th?
It does seriously vary sometimes though. If I'm eating while I'm drinking I can tank a lot of drink for a long period of time, until the end of the night where it all hits at once and things get messy.