This can not be better illustrated than through an example and that is exactly what is going to be done here.
Let’s say you are playing online hold’em and you have a hand of 8, 9 suited in a game with the small blind of $3 and the big blind of $6. Then you call the raise that came from one player and all the other players do that also. There are six players in total in the poker room. So the pot added up to $36 or more from now.
In the flop, the cards you can see are Js , 7h, and 4h.
Now, a difficult decision lies ahead of you. Once you have seen the flop you realize that you have a gutshot to a nuts straight because you are now missing only a 10 from hitting that hand. The idea is to decide whether it is worth it to draw for the nuts or not.
The player in first position bets and the following two players that are stitted before you call. So the pot became somewhere around $45. if you are looking after that gutshot straight then you have to consider the fact that it has 4 outs that are the card you are missing, the 10 in this example. 4 cards out of the total of 47 cards left in the deck. So odds are 4:47. On the river the cards in the deck decrease by one so the odds become 4:46. Simplifying, it turns out that to hit the straight on the turn you have 1:11 chances. The pot odds are in your favor because you now have to call $3 for the amount of $45 accumulated so far.
On the turn, the following cards are placed on the table: 6s, 4h, 7h, Js. This means that you have now the chance to draw to 2 straights and you are hoping for either one of the following cards: a five or a ten. The outs just became 9 for you hand and the odds just improved on your side. Now your odds of hitting the draw are doubled because there are eight outs. And, in addition to that in this case you have the chance of hitting a different hand also, a flush and for that you need any spade card. For the flush there are 9 outs. There is a five of spades and a 10 of spades that are already counted as outs, so they will not be counted again. This basically means that your odds to improve the hand are 9+4:46, meaning 15:46 or about 33% for your draw to hit. This is a pretty good percent and even if the ones situated in front of you bet or raise, you can still get a good pot odd also.
It is crucial for you to learn over time to instantly calculate pot and implied odds both. You have always to calculate you pot odds, based on what is situated now on the table, and then try and think about future bets and recalculate the pod and its odds, this way you get to the true meaning of implied odds.
