The chance the dealer busts, by upcard.
2 about 35%, 3 about 37%, 4 about 40%, 5 about 42%, 6 about 42%, 7 about 26%, 8 about 24%, 9 about 23%, 10 about 21%, A about 12% (S17, 6 decks, before the second card is dealt). This is why you stand against 2–6.