Out (poker)
In a poker game with more than one betting round, an out is any unseen card that, if drawn, will improve a player's hand to one that is likely to win. Knowing the number of outs a player has is an important part of poker strategy. For example in draw poker, a hand with four diamonds has nine outs to make a flush: there are 13 diamonds in the deck, and four of them have been seen. If a player has two small pairs, and he believes that it will be necessary for him to make a full house to win, then he has four outs: the two remaining cards of each rank that he holds.
One's number of outs is often used to describe a drawing hand: "I had a two-outer" meaning you had a hand that only two cards in the deck could improve to a winner, for example. In draw poker, one also hears the terms "12-way" or "16-way" straight draw for hands such as 6♥ 7♥ 8♠ (Joker), in which any of sixteen cards (4 fours, 4 fives, 4 nines, 4 tens) can fill a straight.
The number of outs can be converted to the probability of making the hand on the next card by dividing the number of outs by the number of unseen cards. For example, say a Texas Holdem player holds two spades, and two more appear in the flop. He has seen five cards (regardless of the number of players, as there are no upcards in Holdem except the board), of which four are spades. He thus has 9 outs for a flush out of 47 cards yet to be drawn, giving him a 9/47 chance to fill his flush on the turn. If he fails on the turn, he then has a 9/46 chance to fill on the river. Calculating the combined odds of filling on either the turn or river is more complicated: it is (1 - ((38/47) * (37/46))), or about 35%. A common approximation used is to double the number of outs and add one for the percentage to hit on the next card, or to multiply outs by four for the either-of-two case. This approximation works out to within a 1% error margin for up to 14 outs.
