A straight flush is a hand that contains five cards of sequential rank, all of the same suit, such as Q♣ J♣ 10♣ 9♣ 8♣. It ranks above four of a kind, below a royal flush.
The probability of being dealt a straight flush is 0.0015% or 1 in 649,739.
[1] The probability of being dealt a natural royal flush is the same as that of being dealt any specific hand, which is 0.000154% or 1 in 649,738.[2].When comparing two equal straight flushes, the one with the higher top card is better. If two players have identical straight flushes, they split the pot.
Aces can be high or low so the Lowest straight flush is Ace-2-3 while the highest is 10-Jack-Queen. There are no kickers with straights since all five cards are needed to make the hand.[3]
The odds of being dealt a straight flush in poker are about 1 in 655,000 hands played (assuming no jokers). The probability increases with the number of players because more cards are available to complete the hand. For example, if there are only two players in a hand, the chance of one player being dealt a straight flush is 0.000003%. With three players, it increases to 0.
000028%. With four players, it increases to 0.000102%. The chance becomes more significant as more players are added because more cards end up in play and there are more opportunities for multiple players to make a Straight Flush.[4].
The odds of making a Straight Flush go up significantly when you have wild cards because there are more ways to make a Straight Flush with wild cards. For example, if you have two jokers in a standard 52-card deck and you use them as wild cards, then there are 6 ways to make a Straight Flush: J♦ 10♦ 9♦ 8♦ 7♦; Q♦ 10♦ 9♦ 8♦ 7♦; K♦ 10♦ 9♦ 8♦ 7♦; A♦ 10♦ 9♦ 8♦ 7♦; 5♥ 4♥ 3♥ 2♥ A♥; 6♥ 4♥ 3♥ 2♥ A♥.[5]
The probability of making a Straight Flush goes down when you have less than 5 cards because there are fewer ways to make a Straight Flush with fewer than 5 cards. For example, if you have only 4 cards, then the only way to make a Straight Flush is if you have 4 cards in sequential rank and they are all of the same suit (e.g., 9♠ 8♠ 7♠ 6♠).
The probability of this happening is very low: 0.000024% or 1 in 41,476 hands.[6].
The probability of making a Straight Flush also goes down when you have more than 5 cards because there are more ways to not make a Straight Flush with more than 5 cards. For example, if you have 7 cards, then the chances of not making a Straight Flush go up because there are more possible combinations of ranks and suits that do not result in a Straight Flush (e.g., 7♣ 6♠ 5♥ 4♠ 3♥).
The probability of making a Straight Flush given 7 cards is 0.000015% or 1 in 666,667 hands.[7].
The odds of making a Straight Flush go up when you use wild cards because there are more ways to make a Straight Flush with wild cards. For example, if you use 2 jokers as wildcards in a standard 52-card deck, then there are 6 ways to make a Straight Flush: J♦ 10♦ 9♦ 8♦ 7♦; Q♦ 10♦ 9♦ 8♦ 7♦; K % or 1 in 41.
