I was having a discussion with a colleague and we couldn't recall how they both worked. Does 一人以上 mean a) 1 or more persons or b) more than one person?
According to the Wikipedia article on these two, 以下 and 以上 include the number that precedes them.
If you want to exclude the number on the upper end (instead of 以下) use 未満(みまん).
I had a few different discussions (and taking Ito-san's point below as well) about this - 超 seems to be used (?) but I've never really heard it. In this case we would probably go back to standard grammar using a verb instead:
If there was really a need to exclude a certain number in the case of 以上, you could always add 1 to it -- e.g.
Although that seems strange too. Maybe there's not much of a use for that kind of term?
As makdad and Axioplase stated in their answers, the “correct” usage is that X以上 and X以下 (where X is a number) include X. However, the “incorrect” usage with X excluded is not rare, and therefore it is better to be aware of this possibility, too. For example, when talking about a ski lift, some people may well say:
when they really mean “This lift cannot carry more than one person.”