The 21+3 blackjack side bet uses your first two cards and the dealer’s up-card to form a three-card poker hand. Depending on the paytable, it can pay for hands such as flush, straight, three of a kind, straight flush and suited trips.
This 21+3 Blackjack Side Bet Calculator estimates the return to player, house edge, win probability and expected loss from the paytable you enter. Select the number of decks, choose a preset, or customize every payout to match the exact table you are checking.
Important: side-bet rules and paytables vary by casino. A small payout change, especially on the common flush outcome, can move the house edge sharply. Use this tool as a paytable audit, not as proof that a side bet is profitable.
21+3 Side Bet Calculator
Estimate RTP, house edge and EV from deck count and custom payouts.
| Hand Type | Pays | Probability | Return Contribution | Combos |
|---|---|---|---|---|
| Suited Trips Three identical rank-and-suit cards | -- | -- | -- | |
| Straight Flush Consecutive rank, same suit | -- | -- | -- | |
| Three of a Kind Same rank, not suited trips | -- | -- | -- | |
| Straight Consecutive rank, mixed suits | -- | -- | -- | |
| Flush Same suit, not straight flush | -- | -- | -- |
Enter paytable data to analyze this side bet.
How to Use the Calculator
- Select the number of decks: 21+3 probabilities change with deck count because duplicate cards become possible in multi-deck shoes.
- Choose a paytable preset: start with a common graded paytable, flat 9:1 version, or short-pay variation.
- Edit the payouts: if your table pays differently, change each payout manually.
- Enter your stake: the calculator estimates expected loss per bet and per $100 wagered.
- Check RTP and house edge: lower house edge is better, but most side bets are still worse than the main blackjack hand played with good strategy.
For the main blackjack hand, use the Blackjack Payout Calculator. If you are analyzing card-counting conditions, use the Blackjack True Count Calculator.
What Counts as a 21+3 Winning Hand?
| Hand | Meaning | Why it matters |
|---|---|---|
| Suited Trips | Three identical rank-and-suit cards from multiple decks. | Rare jackpot outcome; impossible in low-deck games without enough duplicate cards. |
| Straight Flush | Three consecutive ranks in the same suit. | Rare but more common than suited trips. |
| Three of a Kind | Three cards of the same rank, not all identical suited copies. | Deck count affects this probability strongly. |
| Straight | Three consecutive ranks in mixed suits. | Usually pays less than straight flush. |
| Flush | Three cards of the same suit, not consecutive. | Often the most important payout because it occurs relatively often. |
Why Paytable Differences Matter
The same 21+3 side bet can have very different value depending on the posted payouts. Casinos can increase the house edge by changing one common hand payout.
The Flush Short-Pay Problem
The flush is one of the more frequent winning outcomes. If a table lowers the flush payout from 5:1 to 4:1, the effect is larger than many players expect because that payout applies to a relatively common event.
This is why the calculator breaks down each hand’s probability and return contribution. A large jackpot payout looks attractive, but frequent low-tier hands often determine most of the RTP.
Example: Graded 100-40-30-10-5 Paytable
A common graded 21+3 paytable pays:
- 100:1 for suited trips
- 40:1 for straight flush
- 30:1 for three of a kind
- 10:1 for straight
- 5:1 for flush
This paytable can be reasonable by side-bet standards, depending on deck count and exact rules. It is still a side bet, so it usually carries a higher house edge than the main blackjack game under basic strategy.
Deck Count and Suited Trips
Deck count matters because multi-deck games contain duplicate cards. For example, there is only one king of hearts in a single deck, so three identical kings of hearts cannot appear. In a six-deck or eight-deck shoe, multiple identical copies exist, making suited trips possible.
The calculator accounts for this by changing the number of possible combinations as deck count changes.
What the Calculator Assumes
- The calculation uses the player’s first two cards plus the dealer up-card as a three-card set.
- The shoe is treated as fresh before those three cards are drawn.
- Payouts are entered as net “to 1” payouts. For example, 5 means 5:1 profit.
- Actual casino rules may classify certain hands differently, so always compare the tool setup with the table rules.
Should You Play 21+3?
Most blackjack side bets are entertainment bets. They add volatility and occasional high payouts, but they usually carry a higher house edge than the main blackjack hand.
| House Edge Result | Interpretation |
|---|---|
| Below 3% | Strong for a side bet, but still not automatically better than the main game. |
| 3%–7% | Typical side-bet territory. Treat mainly as entertainment. |
| 7%–10% | Expensive. Payouts are likely short for the probabilities. |
| 10%+ | Very high house edge. Usually poor value. |
Related Blackjack Tools
- Blackjack Payout Calculator — calculate main-hand payouts.
- Blackjack True Count Calculator — convert running count by deck depth.
- Blackjack Strategy Calculator — check basic-strategy decisions.
- Risk of Ruin Calculator — estimate bankroll survival under repeated betting.
Frequently Asked Questions
What is the 21+3 side bet in blackjack?
21+3 is a blackjack side bet that uses the player’s two starting cards and the dealer’s up-card to form a three-card poker hand.
What hands win in 21+3?
Common winning hands are suited trips, straight flush, three of a kind, straight and flush. Exact payouts depend on the casino’s paytable.
Why does deck count matter?
Deck count changes the number of possible card combinations. Some outcomes, especially suited trips, require enough duplicate cards in the shoe to be possible.
Is 21+3 a good bet?
It depends on the paytable, but most 21+3 versions still have a higher house edge than the main blackjack hand played with correct strategy.
Can I count cards to beat 21+3?
Advanced players have developed suit- and composition-based approaches, but this is more difficult than basic blackjack counting and is not practical for most players.
What payout change hurts the most?
Lowering the flush payout can be especially damaging because flushes occur more often than jackpot hands. Always check the full paytable before playing.
Responsible gambling notice: blackjack side bets are high-variance wagers. This calculator estimates theoretical return from the paytable; it does not predict short-term results or guarantee profit.