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Rummy is a popular blackjack variant found in Costa Rica. Most Costa Rican casinos don't offer blackjack at all, claiming it is illegal. So, if you like 21-based games, and depending on which casino you're in, you may be stuck playing Rummy.


These are what I'm calling the "benchmark rules" for Rummy, which most casinos follow. Some casinos adopt stingier rules; for those instances, see the rule variations section below.

  1. Four to six decks.
  2. An ace and 10-point card count as 21 points. Thus, there is no 3-2 bonus for a winning "blackjack," because there are no blackjacks.
  3. Dealer stands on soft 17.
  4. Double any two cards.
  5. Early surrender.
  6. Double after split allowed.
  7. Re-split any pair, including aces, up to four hands.
  8. Draw to split aces not allowed.
  9. The following bonuses for a three of a kind and straight flush apply to the first three cards of the original hand only.

    Rummy Bonuses

    Player hand Unsuited Suited Total 21
    Three of a kind 3 to 1 5 to 1 5 to 1
    Straight flush n/a 3 to 1 5 to 1
  10. Bonuses pay immediately, even if the third card causes the player to bust.
  11. If the player gets a bonus after doubling, then the bonuses apply to the total amount bet.
  12. Splitting voids any chance of a bonus.
Some casinos of Costa Rica. Click on any image for a larger version.


The following table shows the basic strategy, assuming the rules above. Please note the bonus exceptions for two suited player cards to the right of the table.


House Edge

Assuming the benchmark rules and basic strategy above, the house edge is 1.00%.

Rule variants

The following table shows some rule variants you may see and the effect on the house edge.


Rule Variants

Rule Effect
Draw to split aces -0.17%
4 Decks +0.02%
No re-splitting aces +0.06%
Dealer hits soft 17 +0.16%
No surrender +0.47%

It is interesting to note that the house edge goes up as the number of decks goes down. I assume because it becomes harder for the player to make three of a kind bonuses.


I would like to thank Cindy Liu and CrystalMath for their assistance in this analysis.