So the rules of 2 and 4 are very useful at the table. They give your approximate odds but become inaccurate after I believe 12 outs.
- Use 2 on the flop if you are not being put all-in or calling an all-in
- Use 2 on the turn always
- Use 4 on the flop if you are being put all-in or are calling an all-in
So you use them to find your estimated equity. Once you have that calculated, you then compare it to the pot odds you are being offered.
If you are all-in, your equity should be greater than the pot odds you are being offered for it to be +EV. I say your equity should be larger because if it is equal or a bit under the pot odds it is -EV. Some people would say call if it is equal, but the rake taken after the hand makes it a bit -EV.
If you are not all-in you also need to consider the effect of implied odds. Implied odds state you can call now a bit -EV but expect to make up for that on later streets if you hit your draw and villain will pay you off.
Example Hands Equity
So with both hands you need to consider all of your outs. You are only assuming your flush will win, but an A or K may win as well.
So lets assume for simplicity sake that you need the flush to win and an A or K won't win (in reality they are partial outs, if not full outs in some cases). So we are assuming you have 9 outs like you said for the flush.
Example 1: All-In
So you have approximately 36% equity in the hand, i.e. chance of making your flush draw. But you have to call $1.94 into a $2.07 pot. Since you have to call approximately 50% of the pot,
this is a fold. Your draw equity must be greater than the pot odds to call.
Example 2: Not All-In
Again, you have approximately 18% equity in the hand, i.e. chance of making your flush draw on the turn. Villain donks and gives you 2:1 (33%) pot odds. Well, this is not good pot odds; however, if you think you can make up for that 15% difference in equity on the turn or river to get good pot odds because villain will pay you off, then you should call. If villain is a NIT and will just shut down if the flush hits, then its a fold.
Getting back to your A h K h
So with your hand, on the high end, we can say you have as many as 15 outs to win if an non-heart A or K hits. If that is true,then in hand one with the all-in you should call because with 15% outs you have 54% equity in the hand. Just remember, with 14+ outs you will be happy to call because you are greater than a coin flip favorite to win the hand in the long run.
We will be talking about poker math, pot odds, equity, implied odds, etc in the next installment of the Mastering Holdem Basics series.
Hope this helps clarify some things for you.