What busting means
A hand busts when its total goes over 21. A bust loses immediately, before the dealer plays out the hand. That makes it the main cost of hitting, and the reason many decisions in blackjack are really a question of how much bust risk is acceptable.
The chance of busting depends on the total you hold, and it can be worked out with simple counting. The figures below are for a single card drawn on a hard total, meaning a hand where any ace counts as 1 or where there is no ace. A soft hand cannot bust on one card, because the ace can count as 1 instead of 11.
How the figures are worked out
Use a simplified model: thirteen card values (ace through king), each equally likely, with 10, jack, queen and king all counting as 10. That gives a ten-value on 4 of 13 draws, and each of the other values (ace, 2 through 9) on 1 of 13. In this model an ace counts as 1 when you are on a hard total.
For a hard total of T, you bust if the card drawn is larger than 21 minus T. Count the card values that satisfy this, divide by 13.
Real shoes differ from this model. Cards already seen are gone, which shifts the proportions slightly, and a multi-deck shoe is closer to the model than a single deck. The figures are a good guide to scale, not exact chances for any particular hand.
Bust chance on one card, hard 12 to 21
| Hard total | Cards that bust it | Chance of busting |
|---|---|---|
| 12 | 10-value (4 cards) | 4/13, about 31% |
| 13 | 9, 10-value (5) | 5/13, about 38% |
| 14 | 8, 9, 10-value (6) | 6/13, about 46% |
| 15 | 7 to 10-value (7) | 7/13, about 54% |
| 16 | 6 to 10-value (8) | 8/13, about 62% |
| 17 | 5 to 10-value (9) | 9/13, about 69% |
| 18 | 4 to 10-value (10) | 10/13, about 77% |
| 19 | 3 to 10-value (11) | 11/13, about 85% |
| 20 | 2 to 10-value (12) | 12/13, about 92% |
| 21 | Any card (13) | 13/13, 100% |
A hard 11 or lower cannot bust on one card, since the highest value a card can add is 10 and 11 plus 10 is exactly 21.
The pattern is steady: each extra point of total adds one more bust card, which is about 7.7 percentage points.
Reading the table
A hard 12 busts on about three draws in ten. A hard 16 busts on a little under two out of three. By 17, a hit is more likely than not to bust, and by 20 only an ace saves you.
This is why hitting hard 17 or higher is not part of any standard chart. A hit on 17 has a 9 in 13 chance of busting, and the cards that do not bust it, ace to 4, give totals of 18 to 21 on only 4 of 13 draws, so you could improve, but the rest of the time you lose at once.
It is also why hitting a hard 12 is a real option. A hit on 12 busts less than a third of the time, and many cards leave you with a total of 13 to 21 or a hand you can keep drawing to.
What the figures do not tell you
A low bust chance does not mean hitting is correct, and a high one does not mean standing is. The decision compares the cost of busting with the cost of standing on the current total, which depends on what the dealer is likely to do. A hard 16 busts about 62 percent of the time, yet against a dealer 10 hitting is generally accepted as no worse than standing, because standing also loses most of the time. The reasoning for that hand is explored in the hard sixteen discussion. Likewise, a hard 13 against a dealer 6 is usually stood on, even though the bust chance is only 38 percent, because the dealer’s own bust chance is high.
The table also covers only one card. A hard 12 may need two or more cards to reach a good total, and each extra card adds further bust chance. The overall chance of busting in a multi-card sequence is higher than the first draw alone.
Finally, the figures describe a draw from a shuffled shoe, not a tendency. After you bust, the next hand is no more or less likely to bust than any other. A run of busts does not mean a good hand is coming, which is the gamblers fallacy.
The dealer busts too
The same arithmetic applies to the dealer, who must draw to 16 and stand on 17 or higher. That is why the dealer’s bust rate depends strongly on the upcard, with the dealer bust cards of 2 through 6 being the weakest. A player who understands busting from both sides can see why standing on a low total against a weak card can be right.
The dealer’s bust rate is an advantage the player does not control, and the player’s disadvantage of having to act first, and so busting first, is a central reason a house edge exists. Knowing the numbers helps you lose less, not win.
Keeping it in proportion
Reading the bust table is useful for making decisions based on reasoning instead of fear. It is not a way to predict a particular hand. The casino keeps an edge under standard rules, so only play with money you can afford to lose, set a limit beforehand, and avoid chasing losses. If gambling is causing you problems, a local support service can help.