Blackjack odds and dealer bust rates
The dealer's upcard is the single biggest clue to the right play, because it drives how often the dealer busts.
Short answer
Against a dealer 4, 5 or 6 the dealer busts more than 40% of the time — the weakest upcards on the table. Against a 7 or higher the dealer busts 26% or less, bottoming out at about 12% against an ace. This single table explains most of basic strategy: stand on stiff totals when the dealer is weak, hit them when the dealer is strong.
Dealer bust probability by upcard
These are the bust rates computed by the site's engine for a six-deck game where the dealer stands on soft 17.
| Dealer upcard | Bust probability |
|---|---|
| 2 | 35% |
| 3 | 37% |
| 4 | 40% |
| 5 | 42% |
| 6 | 42% |
| 7 | 26% |
| 8 | 24% |
| 9 | 23% |
| 10 | 21% |
| Ace | 12% |
Against a 4, 5, or 6 the dealer busts more than 40 percent of the time, which is why you stand on stiff totals and let the dealer take the risk. Against a 7 or higher the dealer usually makes a hand, so you hit your stiffs and try to improve. When the dealer hits soft 17 these rates rise for the 6 and the ace, which is why a few surrender and doubling plays change under that rule — see the house-edge page for how much that rule is worth.
Why this drives strategy
Every stand-vs-hit decision on a stiff total (12–16) comes down to comparing your own bust risk against the dealer's. Individual hand pages in the decision library show both numbers side by side — for example, hard 16 vs a dealer 10 shows the dealer busts 23.1% of the time against a 10, while you bust 61.2% of the time if you hit, which is part of why that hand is a surrender rather than a hit.
[TODO: publish overall win / push / loss frequencies and expected rounds-per-hour once that simulation is run through the site's engine; only the engine-verified dealer bust table is shown here.]
Common questions
Why does the dealer bust so much less against a 10 or ace?
Those upcards are already close to a strong total, so the dealer rarely needs risky extra cards to reach 17. Weak upcards like 4, 5 and 6 force the dealer to draw more often, and drawing more often means busting more often.
Does deck count change these numbers?
Deck count has a small effect on exact probabilities but does not change which upcards are weak or strong. The table above is for the common six-deck game.
Should I change my bet based on the dealer's upcard?
Not under basic strategy — the upcard changes your playing decision, not your bet size. Bet-size changes based on a depleted, card-counted shoe are a different skill; see card counting.