The weakest upcards are 5 and 6 (busting about 42–43% of the time). The strongest is the ace, at about 12%.
There is a cliff between 6 and 7 — 42% drops to 26% in one step.
The dealer has no choices
On 16 or less the dealer must draw; on 17 or more the dealer must stop. The procedure is identical even when every player has already busted. Because it is fixed, the upcard alone determines the distribution of outcomes.
| Upcard | Busts | Character |
|---|---|---|
| 2 | about 35% | Somewhat weak |
| 3 | about 37% | Weak |
| 4 | about 40% | Weak |
| 5 | about 43% | Weakest |
| 6 | about 42% | Weakest |
| 7 | about 26% | Strong |
| 8 | about 24% | Strong |
| 9 | about 23% | Strong |
| 10 | about 21% | Very strong |
| A | about 12% | Strongest |
Why 5 and 6 are the weakest
The dealer has to reach 17 before stopping. Starting from a 5 or 6 means drawing several cards to get there, and every one of those draws is another chance to break.
A 6 plus a ten-value card makes 16, and on 16 the dealer must draw again. Any six or higher then busts. Paths like that are common.
Why 7 is suddenly strong
A 7 plus a ten-value card makes 17 on the spot, and the dealer stops. A single card can finish the hand. Since ten-value cards are the most common in the deck, this happens often.
That is the cliff between 6 and 7. Read the chart across and the colours change sharply at exactly this point.
Why the ace is strongest
An ace counts as one or eleven. A dealer holding an ace finds it very hard to bust, because whenever the total would go over, the ace simply drops to one.
An ace plus a ten-value card is also blackjack. So the dealer ace busts only about 12% of the time and is the worst upcard you can face.
This one table explains half the strategy
One sentence runs through the whole chart.
Wait when the dealer is weak; fight when the dealer is strong
Against 2 through 6 you avoid risk and let the dealer break (stand), or you press your bet where you are ahead (double, split). Against 7 through A standing loses anyway, so you accept bust risk to build a hand that can win (hit).
Why hard 13 through 16 stand against 2–6, and why doubling clusters against 3–6, both follow directly from this.
Do not try to compute plays from these numbers alone
Bust probability is where the reasoning starts, not where it ends. A real expected-value calculation also weighs how the dealer's surviving hands are distributed, what cards you are likely to draw, and the blackjack payout.
Hard 12 is the clearest example: a dealer 2 busts 35% of the time, more often than your 31% chance of busting, yet hitting is still correct — because standing on 12 concedes the 65% of hands where the dealer survives. The full argument is in the hard 12 explainer.
So treat this table as a tool for remembering the chart, not a replacement for it.
H17 shifts things slightly
Where the dealer draws on soft 17, there is one more opportunity to bust, so bust probability rises a little. It is still worse for the player, because the dealer more often improves from 17 to 18, 19, 20 or 21. See the rules page.