Blackjack side-bet math
How 21+3 works
21+3 combines the player’s first two cards with the dealer’s up card. Those three cards form a poker-style hand that settles separately from the main blackjack wager.
Qualifying hands
All three cards share a suit.
Three consecutive ranks; suits may differ.
All three cards share a rank.
Three consecutive ranks in the same suit.
Queen-king-ace in the same suit.
The same rank and suit repeated from multiple decks.
A normal five-card royal flush cannot occur with only three cards. Some tables market suited queen-king-ace as a “mini royal”; the app identifies it separately and applies the selected table’s payout.
An example tiered paytable
| Hand | Example payout |
|---|---|
| Suited three of a kind | 100:1 |
| Straight flush or mini royal | 40:1 |
| Three of a kind | 30:1 |
| Straight | 10:1 |
| Flush | 5:1 |
Other tables use different schedules, including flat payouts for any qualifying hand. The label “21+3” is not enough to determine the return; you must inspect the posted paytable.
Why deck count appears in the lab
In a multi-deck shoe, identical rank-and-suit cards can coexist. That makes suited three of a kind possible and changes the exact fresh-shoe probabilities. The app enumerates every physical three-card combination for the selected number of complete decks.
Keep the two wagers separate
A 21+3 win does not make hitting, standing, doubling, splitting, or surrendering more or less correct. Main-hand basic strategy still depends only on the player hand, dealer up card, available actions, and table rules.