Around 5. I know surveys always come out with more than that, but I suspect that's largely because the only people bothered about completing the surveys are the ones who are really into sex.
I know I was at a party at what was considered a fairly sexually active uni according to all these various surveys, but when someone targeted a girl in a game of I Have Never with "I have never slept with 18 people" everyone was genuinely shocked when she drunk, with even the most studly of people in the room proclaiming they'd only slept with 8 or so.
To balance these I know plenty of people who, at uni, have slept with 0/1 people.