Super Fun 21: Nine Gifts and One Very Large Bill
Updated
Surrender whenever you like. Double on any number of cards. Six cards without busting wins on the spot. Your 21 always beats the dealer's. Every one of those is real, and every one of them is paid for by a single line: blackjack pays even money, which costs you 2.27%.
- Blackjack pays 1:1, not 3:2. That alone costs 2.27%.
- A blackjack in diamonds pays 2:1, which gives back 0.28%.
- Eight generous rules give back the rest, and we priced each one.
- Published house edge: 1.16% single deck, 1.40% six decks.
- We compute 0.71% for six decks — and the gap is not a mistake. See below.
The whole ledger, one rule at a time
We started from a six-deck game where the dealer hits soft 17 and blackjack pays even money, then switched on each Super Fun 21 rule in turn. Each row is the running house edge after that rule is added.
| Rule added | House edge | Worth |
|---|---|---|
| Six decks, H17, blackjack at 1:1 | 2.882% | — |
| Blackjack in diamonds pays 2:1 | 2.599% | 0.283% |
| Player 21 and player blackjack always win | 1.809% | 0.790% |
| A 21 of five or more cards pays 2:1 | 1.585% | 0.224% |
| Six cards totalling 20 or less wins outright | 1.404% | 0.181% |
| Double on any number of cards | 1.219% | 0.185% |
| Surrender half your bet after doubling | 1.110% | 0.109% |
| Late surrender at any point | 0.981% | 0.129% |
| Hit, double and re-split split aces | 0.714% | 0.267% |
Two things stand out. The first is how much of the giveback comes from one rule: a player 21 always winning is worth 0.790%, more than three of the flashier rules combined. It is also the rule nobody notices, because it only shows up on hands where you would otherwise have pushed.
The second is the diamond blackjack, which is a nice piece of arithmetic. Given that you have a blackjack at all, the chance it is entirely in diamonds is exactly one in sixteen — a quarter for the ace, a quarter for the ten-value card — so the average blackjack pays 1.0625 rather than 1.00. That works out to 0.283%, and it is the only rule in the game you can price in your head.
Why our number is lower than the published one
We compute 0.714% for six decks. The published figure is 1.40%. That is a large gap and it deserves a straight answer rather than a footnote. There are two causes, and we can put a size on both.
First: the published figure is a simulation of basic strategy. Wizard of Odds says so explicitly — random simulation, cut card, following the charts on that page. A basic strategy chart is a table of totals. But in Super Fun 21 the right play often depends on how many cards you are holding: a sixth card that keeps you at 20 or less wins outright, and a fifth card that makes 21 pays double. No chart organized by total can express “hit this 16 because it is your fifth card”. Our engine tracks the card count and plays accordingly, and in a game built around long hands that is worth a great deal.
Second: our model slightly overstates long hands. It draws each card from a fixed shoe composition rather than removing cards as they come out. We measured the error directly — the probability of reaching six cards without busting:
| Shoe | Hand | Our model | With removal | Overstated |
|---|---|---|---|---|
| One deck | 2-2 | 0.05264 | 0.04685 | 12.4% |
| One deck | 3-4 | 0.02227 | 0.01839 | 21.1% |
| One deck | 2-10 | 0.00214 | 0.00135 | 58.1% |
| Six decks | 2-2 | 0.06645 | 0.06545 | 1.5% |
| Six decks | 3-4 | 0.02488 | 0.02423 | 2.7% |
| Six decks | 2-10 | 0.00240 | 0.00225 | 6.3% |
That is why our single-deck figure (0.38%) is relatively further from the published 1.16% than our six-deck one: the error is an order of magnitude larger in one deck, where every card you take really does change what is left.
Use the published figure to plan around. 1.40% is what the game costs a good chart player at a six-deck table. Our 0.71% is a floor that assumes you count your own cards and never make a mistake, and it is optimistic even then.
Is it a good game?
No, and the reason is the one at the top. Even money on a blackjack is the most expensive single rule in common use — worse than a dealer hitting soft 17, worse than losing double-after-split, worse than eight decks instead of six. Super Fun 21 buries it under eight cheerful rules and a name, but the arithmetic does not care how it is packaged.
It is also the same trick as a 6:5 table, taken further. A 6:5 game pays your blackjack 1.2 to 1; this one pays 1 to 1. The difference is that 6:5 gives you nothing in return and Super Fun 21 gives you a great deal — just not quite enough.
For a counter it is poor for the same reason it is poor at Blackjack Switch: a large part of what a rich shoe is worth comes from being paid 3:2 on the extra blackjacks it produces. Take that away and the count has much less to reward.
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By Martin Kosek · every number on this site is computed by us, not copied.
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