What is 21+3 in blackjack?
21+3 is a blackjack side bet that uses your two initial cards combined with the dealer’s upcard to form a three-card poker hand. If the combination produces a qualifying poker hand you win the side bet, regardless of the blackjack outcome.
Qualifying hands
A flush (all three cards same suit) typically pays 5:1. A straight (three consecutive ranks) pays 10:1. Three of a kind (three cards of the same rank, different suits) pays 30:1. A straight flush (consecutive and same suit) pays 40:1. A suited three of a kind (three identical cards) pays 100:1 or higher at some tables.
Expected value
The house edge on 21+3 ranges from about 3% to 10% depending on the payout table version the casino uses. Suited three of a kind is extremely rare but the big payout is what draws players in. Like most side bets, 21+3 costs more in the long run than the main game but adds a layer of interest beyond the standard hand outcome.