Poker odds fordummies

To Calculate Odds You First Need The Number Of Winning Cards, Or "Outs"

Part3
Using The "Outs" To Calculate Texas Hold'em Poker Odds
We have already determined that you have nine "outs". Now there are 52 cards in a deck and two of those are in your hand, leaving 50. In addition, there are four cards exposed from the flop and turn, leaving 46 cards. Although your opponent is holding two others we ignore those. Our calculations in Internet Texas Hold'em poker are only based on the cards you can see and what could be left in the deck.
With nine outs and 46 cards unknown, there are nine cards that will let you win the hand and 37 cards (46 unseen cards - 9 winning cards) that will cause you to lose. Thus the odds of you getting one of the cards you need on the river are 37 to 9. This simplifies down to just about 4:1. In other words, you are four times more likely to lose this pot than you are to win it.
First Calculate How Many Cards From The Deck You Can't See:

The Unseen Cards Are Then Split Into Winners And Losers:
37Cards in the deck that will still cause you to lose

9Cards in the deck that will give you a win

Your Odds of Getting The Winning Flush Are therefore:37 to 9This Simplifies Down To:4:1(or 20% for those that like to use percentages)In other words, you are 4 times more likely to lose this pot than you are to win it.
Part4
The BIG Question - Should You Call The Bet?
So we have odds of around 4:1 to win this hand. To decide whether or not we should call our opponent's bet depends on how much money is in the pot. No, we don't mean that if there's a whole bunch of cash you should just go for it. What you should be looking for is the ratio of money you could win compared to the size of your opponent's bet.
OK, we'll continue our example. Let's say there was $90 in the pot and your opponent bets $10. That makes a total of $100 in the middle of the table just waiting to be won. You need to match your opponent's bet of $10 to see the river card, so it's going to cost you $10 to see if that last card is going to be one of the nine you need to win.