A poker player is drawing if they have a hand that is incomplete and needs further cards to become valuable. The hand itself is called a draw or drawing hand. For example, in seven-card stud, if four of a player's first five cards are all spades, but the hand is otherwise weak, they are drawing to a flush. In contrast, a made hand already has value and does not necessarily need to draw to win. A made starting hand with no help can lose to an inferior starting hand with a favorable draw. If an opponent has a made hand that will beat the player's draw, then the player is drawing dead; even if they make their desired hand, they will lose. Not only draws benefit from additional cards; many made hands can be improved by catching an out – and may have to in order to win.

An unseen card that would improve a drawing hand to a likely winner is an out. Playing a drawing hand has a positive expectation if the probability of catching an out is greater than the pot odds offered by the pot.

The probability ${\displaystyle P_{1}}$ of catching an out with one card to come is:

The probability ${\displaystyle P_{2}}$ of catching at least one out with two cards to come is:

A dead out is a card that would normally be considered an out for a particular drawing hand, but should be excluded when calculating the probability of catching an out. Outs can be dead for two reasons:

A flush draw, or four flush, is a hand with four cards of the same suit that may improve to a flush. For example, K♣ 9♣ 8♣ 5♣ x. A flush draw has nine outs (thirteen cards of the suit less the four already in the hand). If a player has a flush draw in Hold'em, the probability to flush the hand in the end is 34.97 percent if there are two more cards to come, and 19.56 percent (9 live cards divided by 46 unseen cards) if there is only one more card to come.

An outside straight draw, also called up and down, double-ended straight draw or open-ended straight draw, is a hand with four of the five needed cards in sequence (and could be completed on either end) that may improve to a straight. For example, x-9-8-7-6-x. An outside straight draw has eight outs (four cards to complete the top of the straight and four cards to complete the bottom of the straight). Straight draws including an ace are not outside straight draws, because the straight can only be completed on one end (has four outs).

An inside straight draw, or gutshot draw or belly buster draw, is a hand with four of the five cards needed for a straight, but missing one in the middle. For example, 9-x-7-6-5. An inside straight draw has four outs (four cards to fill the missing internal rank). Because straight draws including an ace only have four outs, they are also considered inside straight draws. For example, A-K-Q-J-x or A-2-3-4-x. The probability of catching an out for an inside straight draw is half that of catching an out for an outside straight draw.