Different Rules

Not all blackjack tables are the same. Casinos tweak the rules, and each tweak shifts the odds — sometimes by a little, sometimes enough to turn a good game into a bad one.

The main rule variations

• Number of decks — single-deck games deal a natural slightly more often; eight-deck shoes dilute the effect of removal.
• Dealer hits or stands on soft 17 (H17/S17) — H17 costs the player roughly $0.2\%$ in expected value, because the dealer gets a second chance to improve a hand that cannot bust.
• Double after split allowed (DAS) — worth about $0.14\%$ to the player, since some pairs become much more profitable when doubling is available.
• Blackjack payout — the big one. A natural paying $6{:}5$ instead of $3{:}2$ costs around $1.4\%$, more than almost any other single rule.

Why strategy depends on the rules

Basic strategy is not one table but a family of tables. Removing the option to double after splitting changes what is optimal for a pair of $8$s; a dealer who hits soft 17 makes standing on soft 18 against a $6$ correct instead of marginal. Whenever you sit down, check the placard listing the rules first — the cheapest seats are rarely the best games.