21+3 is an optional blackjack side bet based on three cards: the player’s first two cards and the dealer’s initial face-up card. Those cards are evaluated as a three-card poker hand. The side bet is normally settled before the player hits, stands, doubles, splits, or surrenders.
The name joins the blackjack target of 21 with the three cards used for the bonus wager. It does not mean the three cards must total 21.
What wins
The exact categories and payouts must be read from the table’s posted rules. A common form recognizes:
- straight flush;
- three of a kind;
- straight;
- flush.
Some commercial versions use additional categories such as suited three of a kind, or pay different amounts for the same category. The words “21+3” therefore identify the wager structure, not one universal paytable.
The side wager has no effect on the main blackjack result. A player can:
- win 21+3 and lose the blackjack hand;
- lose 21+3 and win blackjack;
- push the main hand while the side bet wins or loses;
- receive a qualifying side-bet hand even though the blackjack total is poor.
The two wagers share cards, but they are separate contracts.
How the three cards are ranked
A straight uses three consecutive ranks. An ace may be high in queen-king-ace or low in ace-2-3 when the posted rules allow it. A flush uses three cards of the same suit. Three of a kind requires the same rank on all three cards. A straight flush satisfies both the straight and flush conditions.
The ranking order matters because only the highest qualifying category is paid. For example, three consecutive cards of one suit are a straight flush, not both a straight and a flush paid separately.
Multiple-deck blackjack creates combinations impossible in a single deck. Three identical ranks can include duplicated cards from different decks, so deck count changes the probability of three of a kind. That is one reason a published edge should always state the number of decks assumed.
A current official example
Massachusetts’ active blackjack rules allow a casino to offer 21+3 using the player’s first two cards and the dealer upcard. The rules list two minimum paytables:
| Qualifying hand | Table A | Table B |
|---|---|---|
| Straight flush | 9 to 1 | 30 to 1 |
| Three of a kind | 9 to 1 | 20 to 1 |
| Straight | 9 to 1 | 10 to 1 |
| Flush | 9 to 1 | 5 to 1 |
Table A gives one price to every qualifying hand. Table B pays much more for the rarest result but much less for the relatively common flush. The large top number in Table B does not reveal the overall value.
The rules also require the paytable to be selected and posted, and state that the side wager has no bearing on other blackjack wagers.
An eight-deck probability example
The following calculation assumes:
- eight standard 52-card decks;
- three cards drawn without replacement;
- no jokers;
- the category order shown above;
- ace usable high or in ace-2-3;
- no extra category such as “suited trips.”
Under those assumptions, the approximate probabilities are:
| Result | Probability | Rough frequency |
|---|---|---|
| Straight flush | 0.2063% | 1 in 485 |
| Three of a kind | 0.5413% | 1 in 185 |
| Straight | 3.0947% | 1 in 32.3 |
| Flush | 5.8841% | 1 in 17.0 |
| No qualifying hand | 90.2736% | About 9 in 10 |
The total win probability is about 9.7264%, or roughly one qualifying result in 10.3 hands. That hit rate alone still does not reveal the house edge; the payouts must be applied to each category.
How a paytable creates the edge
Expected value is:
EV = Σ(probability of result × net result)
For a one-unit wager:
- a winning category contributes its probability multiplied by the posted net payout;
- a non-qualifying hand contributes its probability multiplied by −1.
Using the eight-deck assumptions above:
Table A
Every qualifying hand pays 9 to 1.
EV = 9 × 0.097264 − 1 × 0.902736 ≈ −0.02736
That is an approximate 2.74% house edge.
Table B
The four categories pay 30, 20, 10, and 5 to 1.
EV ≈ −0.12891
That is an approximate 12.89% house edge.
The same named side bet moves from a relatively moderate side-bet edge to a much more expensive one solely because the paytable changes. Deck count or different category rules would alter both figures.
The active Massachusetts blackjack rules provide the category definitions, settlement timing, and Table A/Table B payouts used in this example. The probability and expected-value calculations above are derived from those rules under the stated eight-deck assumptions; they are not a claim that every 21+3 table uses eight decks or either paytable.
Worked session cost
Suppose a player wagers $5 on 21+3 for 80 hands.
Total side-bet action = $5 × 80 = $400
At a 2.74% edge:
Expected loss ≈ $400 × 0.0274 = $10.96
At a 12.89% edge:
Expected loss ≈ $400 × 0.1289 = $51.56
Both sessions can finish ahead or behind by much more than those amounts. Expected loss is the long-run average cost of the action, not a prediction of the next 80 hands.
The comparison shows why checking the paytable matters more than remembering the brand name.
It does not improve blackjack strategy
The dealer upcard used for 21+3 is already visible when the player later makes the blackjack decision, but the side-bet result does not change basic strategy. Basic strategy still depends on the main hand, dealer upcard, deck and rule package.
A player who receives a 21+3 flush may still need to hit a weak blackjack total. A player who misses the side bet may still hold a strong double-down or split decision. Protecting the bonus cards as if they make the main hand special is a common mental error.
The side bet also does not become favorable because several qualifying hands have not appeared recently. Cards are dealt without replacement within the shoe, so exact composition changes slightly, but casual streak tracking is not a practical substitute for complete composition data and a verified advantage calculation.
Settlement order protects both wagers
Because 21+3 is decided from the first three specified cards, the dealer can settle it before the player hits, doubles, splits, or surrenders the blackjack hand. Keeping the side bet physically and procedurally separate prevents a winning bonus from being confused with the main wager. A dispute should therefore identify which wager, paytable, card combination, and settlement step is actually in question.
What to check before placing it
Before betting 21+3, read:
- the qualifying categories;
- the payout for every category;
- the number of decks;
- whether ace-2-3 and queen-king-ace both count as straights;
- whether an extra category such as suited trips exists;
- whether the payout is stated “to 1” or as total return;
- the side-bet minimum and maximum;
- whether a progressive contribution or separate jackpot condition applies.
Do not infer the rules from another casino, an online version, or a table with the same logo.
Why players remember it
The main blackjack game produces many ordinary wins and losses. A 21+3 hit is rarer, often paid separately, and may be announced or verified in a way that attracts attention. That makes it easier to remember than dozens of losing side wagers.
The memory is real; the accounting is incomplete unless every attempt is counted.
For a direct game-level explanation, continue to 21+3 Explained. For the broader category, see Side Bet. To price repeated action, use Expected Loss and Why Side Bets Make Small Games Expensive.