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Best of Alan Krigman

Gaming Guru

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Fewer Decks at Blackjack Offer Players More

8 May 2001

Casinos deal blackjack from caches of cards comprising various numbers of decks. Games utilizing eight decks are most often encountered, six are also relatively common, and four or fewer are rare and on the endangered species list but not yet extinct.

Some solid citizens assume that number of decks in action is of concern only to card counters, who base decisions on the probability changes that occur as high or low ranks are withdrawn and therefore no longer available. Other bettors believe that since eight deck shoes are "standard," downward departures must be designed to milk more money from the masses. Certain less paranoid but equally gullible gamblers eschew fewer decks because dealers shuffle more often and this slows down the game.

Other things being equal, fewer decks lower the edge all players must fight. Still, some truths infiltrate the above fallacies.

  • Fewer decks are of particular interest to card counters because, in addition to the better base, favorable windows of opportunity are more liable to occur. However, casinos use simple means to void the counters' advantage. Mainly, they discourage counters by narrowing the limits on bets and decreasing the number of cards dealt before shuffling.
  • Fewer decks are intended to drop more dollars onto the bottom lines of the establishments' balance sheets. They achieve this, despite reduced house advantage, by attracting additional players and bigger bets to more favorable games.
  • Fewer decks do mean more shuffles over a given interval. But this factor hurts the casinos as much as it annoys bettors. And the effect is mitigated somewhat because smaller stacks of cards can be shuffled faster. Further, the delays are a small price to pay -- like waiting in a long dessert line at the all-you-can-eat buffet for an elegant Baked Alaska made-to-order rather than grabbing the workaday ready-made artificial lime-flavored gelatin from the quick-pick rack.

Here's the impact on edge of the number of decks in the game. As a reference, I'll stipulate no resplitting pairs and no surrender but doubling allowed on any initial two cards and after splits.

For every $100 bet at the start of a round by players who adhere strictly to basic strategy, the edge amounts to $0.44 for eight decks, $0.42 for six, $0.36 for four, and $0.19 for two. In a one-deck game with these rules, edge shifts to favor players, and is equivalent to $0.15 per $100 bet. The latter, by the way, is why one-deck games generally restrict doubling or impose such player-unfriendly rules as "dealer hits soft 17" -- which represents a penalty of $0.19 per $100 bet in an of itself at a one-deck table, and $0.20 at six- and eight-deck games.

Much of the gain from fewer decks arises because blackjacks become more common -- contrary to the popular but mathematically unsound "logic" that reducing the number of aces trims the chances of these hands. And, although the dealer and the player are equally apt to get naturals, more blackjacks favor bettors because losses only cost one unit while wins pay one and a half.

Proper doubling situations are also more common in games with fewer decks. On soft hands, for instance, this option is worth over $0.13 per $100 bet in a game with one deck, and $0.04 less with eight decks. Circumstances when splitting benefits the player occur more often in games with more decks, and temper the effect of number of cards somewhat. The impact is greatest when resplitting is allowed. However, the difference associated with splits and resplits is low enough so this factor doesn't come close to outweighing the gains on blackjacks and doubles. Specifically, correct splits and resplits are worth $0.39 per $100 bet with one deck and only $0.03 more with eight decks.

Maybe you think pennies of edge per $100 bet isn't enough to sway your choice of tables or casinos. Or maybe you think I just make up all these numbers. If so, head for the gelatin, opening the Baked Alaska line for us epicureans. While you're at it, ponder this epigram from the poet, Sumner A Ingmark:

Though eons of tradition frame gamblers' intuition,
Casino superstition is worthy of suspicion.

Alan Krigman

Alan Krigman was a weekly syndicated newspaper gaming columnist and Editor & Publisher of Winning Ways, a monthly newsletter for casino aficionados. His columns focused on gambling probability and statistics. He passed away in October, 2013.
Alan Krigman
Alan Krigman was a weekly syndicated newspaper gaming columnist and Editor & Publisher of Winning Ways, a monthly newsletter for casino aficionados. His columns focused on gambling probability and statistics. He passed away in October, 2013.