Outs in Poker
A card that gives you the better hand is called „out“. If you know how many outs you have, you can estimate the odds to win and decide how to proceed with your hand. You only need two small tools:
The deck of cards
Such a deck consists of 52 cards. You only know 7 of those 52 cards (the two hole and the five community cards on the board). You know 5 of those 52 cards on the flop, on the turn 6 and on the river 7.
The deck is divided into four suits (spades, diamonds, clubs and hearts) which add up to four times 13 cards. There are four cards of each kind, for instance four aces, four tens, four fours etc.
In order to find out the amount of outs, you need to know how many of those cards would give you the best hand. If you have AK and you think you’ll win if an ace or king appears on the turn or river then you have got six outs. (Three from the four remaining aces plus three from the four remaining kings.)
If you have 44 and there's no four on the flop you need another 4 to win. You already have two fours thus there are two fours still left in the deck. Therefore, you have two outs.
Now you have 98 and the flop is 76A. How many outs do you have? Every ten gives you a straight as well as every five. There are four cards each left in the deck, giving you 8 outs.
If you have suited hole cards like 87 of diamonds and there are two of these suits in the flop, then you have a so-called flush draw. There are 13 cards of one suit, the player already has four of them: 13 – 4 = 9. 9 cards give you the flush thus you have 9 outs.
This isn't that difficult, is it? Just remember how a card deck looks like and then count the cards that would improve your hand significantly.
The chance of winning
If you know your outs, you also know the likelihood of hitting one of those outs. Of course it's more likely to hit 15 outs than just 2.
There's an easy way to find out your chances of winning, the so-called „2 and 4 rule“:
You take the amount of your outs and multiply them by 2 to find out the percentage to hit one of your outs with the next card. For instance, you have 9 outs on the turn and you want to know how likely it is to make your hand on the river. 9 x 2 = 18 %. That means that you hit your outs 18 % of the time and miss 82 % of the time. With 4 outs there's an 8 % chance, with 15 outs, 30 %, and so on.
This rule is only true if there's one card to come. Supposing, you're on the turn with 9 outs, you have an 18 % chance of improving. Or if you're on the flop with 9 outs, you hit one of your outs on the turn (!) 18 % of the time.
But if you're sitting on the flop and there are two cards to come you can hit your outs twice (on the turn and the river). Then the calculation changes and you have to multiply your outs by four (completing the 2 and 4 rule).
Supposing your opponent is moving all-in on the flop and you're on a draw. You have to know the amount of outs and the chance of winning. If you want to know your chance of winning from the flop to the river you have to multiply your outs by 4 (instead of 2).
If you have a flush draw on the flop and want to know the likelihood of being ahead on the river, you take your 9 outs and multiply them by 4, giving you a 36 % chance of winning.
Supposing you opponent puts you all-in on the flop, making sure that you see both the turn and the river card and you have an inside straight draw plus one over card, giving you 7 outs. 7 x 4 = 28 %.
To sum it up:
Chance of winning with the next card:
Outs x 2
Chance of winning with the next two cards:
Outs x 4
"Poker is a game of people... It's not the hand I hold, it's the people that I play with."
"Look around the table.  If you don't see a sucker, get up, because you're the sucker."
"Nobody is always a winner, and anybody who says he is, is either a liar or doesn't play poker."
"They anticipate losing when they sit down and I try my darndest not to disappoint one of them."