[asdf1234]

These are only approximations using random hands, which is not necessarily the case in real life.

If you have something like 7 [img]/forums/images/icons/spade.gif[/img] 6 [img]/forums/images/icons/spade.gif[/img] and the board is
K [img]/forums/images/icons/spade.gif[/img] J [img]/forums/images/icons/spade.gif[/img] 4 [img]/forums/images/icons/diamond.gif[/img]
then the chances of a single opponent holding a flush draw as well is 3.33%. If you extend this to 9 opponents, then it increases to 26.27%. It decreases 2-3% for each opponent you lose. Of course, the likelihood is probably less, because the king and jack are both out there, and people are less likely to play trashy suited cards, but we're not taking that into account anyway.

As far as the number of flush draws that will beat you, I'm sure you know, that if there is one out there, it's probably beating you. There are 36 other combinations of hands that can be drawing for a flush and 30 of them beat you. The chance that there is another flush draw out there and that it beats you is 2.77% for a single opponent up to about 23.4% for nine. Again, this decreases 2-3% for each opponent you lose.

These calculations are not exact because they don't take into account situations where multiple opponents hold flush draws, some players have one of the suit, but this is relatively close.