The blackjack house edge
Blackjack is not one game. The same basic strategy meets a different house edge depending on the rules on the felt.
Short answer
With six decks, the dealer standing on soft 17, double after split, and late surrender, the house edge is about 0.39% with correct basic strategy. The same game at eight decks is about 0.41%, and at two decks about 0.18% — fewer decks favor the player. Every rule change moves this number by a fraction of a percent; the table below shows which ones matter most.
What each rule is worth
Starting from the six-deck, dealer-stands-on-soft-17 baseline, these are the individual rule effects this engine computes:
| Rule | Effect on house edge |
|---|---|
| Dealer hits soft 17 | +0.20% worse for you |
| Double after split allowed | 0.12% better |
| Late surrender allowed | 0.07% better |
| Two decks instead of eight | 0.23% better |
Deck count and the soft-17 rule move the number the most. A single-table game with the dealer standing on soft 17 is the best commonly-spread rule set; an eight-deck shoe with the dealer hitting soft 17 is among the worst.
Why the edge is so small
Basic strategy removes almost all of the edge that guessing gives away. Every recommendation is drawn from a combinatorial engine that computes the exact dealer outcome distribution from the upcard, accounting for the dealer's peek for blackjack, then works out the expected value of every option at every future total. The same math grades the trainer and builds the decision library, so the number you see here can never drift from the play you are graded against.
[TODO: publish the exact edge for additional rule combinations (e.g. single-deck H17, no-surrender variants) once run through the engine; only the rule effects already measured are shown here.]
Common questions
What rule set should I look for at a real table?
Fewer decks, the dealer standing on soft 17, double after split allowed, and late surrender offered — in roughly that order of importance. Any one of these missing is a small cost; several missing at once compounds quickly.
Does blackjack paying less than 3:2 change this?
Yes, substantially — a reduced blackjack payout (such as 6:5) adds well over a percentage point to the house edge on its own, more than every rule in the table above combined. Avoid these games.
Is 0.39% good for a casino game?
It is one of the lowest edges on the floor with correct basic strategy, competitive with (or better than) most other table games covered on this site.