Elementary Pot Odds Question

[goodfelladh]

Hey all, any help with this quick question would be appreciated...

Calculating pot odds isn't really a problem for me -- I've committed many of the more common odds/situations to memory so that I don't have to worry about doing a lot of calculations at the table. The issue I am having is deciding which odds I should use in certain situations. For example:

I flop four to a flush. Now I know that I am at 1.86-to-1 dog to make my flush on the turn and river. But I am a 4.11-to-1 dog if I only consider making my flush on the turn. So would I need to be getting better than 1.86 or 4.11 to 1 in order to call in this situation? The 4-1 seems to make more sense to me, but I'm not totally sure.

Also, if I were to use the 1.86-to-1 number, what odds would I need to call a bet if I missed on the turn, because haven't I already committed myself to the river if I used this 1.86-to-1 odds on the flop?

Any help his appreciated. I did a search and found a lot of good information on pot odds, but this issue is still confusing me.