The 21+3 Side Bet: Blackjack's Three Card Poker Tax
Last reviewed: August 2026
21+3 bolts a Three Card Poker hand onto your blackjack: your two cards plus the dealer’s upcard form a three-card hand, and flush-or-better pays. It’s the most popular side bet in blackjack, and a case study in paying carnival prices at a discount table.
How it works
Before the deal, place the side bet. If your first two cards and the dealer’s upcard make a flush, straight, three of a kind, or straight flush, you’re paid, most commonly a flat 9 to 1 on any qualifying hand.
From the three-card math: flush 4.96%, straight 3.26%, trips 0.24%, straight flush 0.22%, about 8.7% of hands qualify (multi-deck shifts these slightly). Paid 9:1, the result on the common six-deck, 9-to-1 version is a house edge of about 3.2%.
The context that matters
You’re sitting at a table where your main bet, with basic strategy, costs about 0.5%. The side bet charges six times that rate. A $5 21+3 alongside a $15 blackjack bet roughly doubles your expected hourly loss at the table while adding a sixth to your action.
| Bet | Edge |
|---|---|
| Blackjack main bet (basic strategy, 3:2) | ~0.5% |
| 21+3 (9:1 flat version) | ~3.2% |
| Tiered 21+3 versions (100:1 suited trips etc.) | ~3 to 7%, paytable-dependent |
The tiered versions with the 100:1 headline are usually worse; the big number is financed by trimming the common payouts.
Is it ever defensible?
As entertainment, it’s mid-pack: cheaper than most slot spins and baccarat side bets, pricier than everything on the craps line. If the sweat of a three-card flush genuinely adds fun, keep it to a fraction of your main bet and know its price. Just never confuse it with the good bet you’re sitting at the table for.
The main game is the discount: protect it with basic strategy, and drill it free.