Five playing cards forming the poker straight flush hand. Green background. A straight flush is a hand that contains five cards in sequence, all of the same suit. This is the diamonds suit straight flush. In five card poker, there are 40 possible straight flushes, including 4 royal flushes. The probability of this hand is almost improbable and equals about 0.0015%. The probability of straight flush is also expressed as odds: 75, 000 to 1. Good luck to you!