The Spanish 21 house edge
Every rule in Spanish 21 has a price. Here is what each one is worth, measured rather than asserted.
Short answer
With six decks, correct play and the full standard rule set, the Spanish 21 house edge is 0.495% of the opening bet when the dealer stands on soft 17, and 0.893% when the dealer hits soft 17 SIM. Because doubles and splits add money to the table, the edge measured against total money wagered, the element of risk, is lower: 0.434% and 0.783%.
The two headline numbers
| Rule set, six decks | House edge per opening bet | 95% confidence interval | Element of risk |
|---|---|---|---|
| Dealer stands on soft 17 | 0.495% | 0.472% to 0.518% | 0.434% |
| Dealer hits soft 17 | 0.893% | 0.870% to 0.916% | 0.783% |
Each figure is the mean of 100,000,000 simulated rounds of the published strategy, dealt from a freshly shuffled six-deck Spanish shoe. SIM
The dealer hitting soft 17 costs about 0.40 percentage points. It is the single most important line on the felt and the first thing to check before sitting down.
What each rule is worth
Each row below is the house edge measured with that one rule removed and everything else, including the strategy, held fixed. The difference from the baseline is what the rule is worth to you.
| Rule removed | Edge, stands soft 17 | Cost to you | Edge, hits soft 17 | Cost to you |
|---|---|---|---|---|
| Nothing removed (baseline) | 0.47% | baseline | 0.87% | baseline |
| Bonus 21s not paid | 0.80% | 0.33 pts | 1.20% | 0.33 pts |
| Player 21 no longer always wins | 0.79% | 0.32 pts | 1.19% | 0.32 pts |
| Doubling limited to two cards | 0.64% | 0.17 pts | 1.05% | 0.18 pts |
| No double-down rescue | 0.61% | 0.15 pts | 0.98% | 0.11 pts |
| No late surrender | 0.47% | 0.00 pts | 0.88% | 0.02 pts |
Each cell is 25,000,000 rounds on a common random seed, so the rows are directly comparable. The published strategy is held fixed across rows, so each cost is the value of the rule to a player who does not re-optimize. SIM
Reading the table
Three things follow from those numbers.
First, the bonus 21s and the always-wins-21 rule are together worth about 0.65 percentage points. They are not a gimmick. They are most of what makes the game playable. A table that has quietly trimmed the bonus pay table is not offering Spanish 21 at the edge quoted here.
Second, doubling freedom and rescue are worth another 0.32 points combined, and both are skill rules. A player who never doubles a three-card hand and never rescues is playing a game with a house edge above 0.8% while believing they are playing a 0.5% game.
Third, late surrender is worth almost nothing under correct play, because the correct chart almost never uses it. Do not choose a table for it.
Spanish 21 against blackjack
A common six-deck blackjack game where the dealer stands on soft 17, with double after split and no surrender, runs an edge near 0.4%. Spanish 21 with the full rule set runs 0.495%. They are close enough that the individual table rules decide which is better. If the blackjack table pays 6:5 on blackjack, Spanish 21 wins easily. If the Spanish 21 table hits soft 17 and the blackjack table does not, blackjack wins.
What is priced here and what is not
The figures on this page cover: six decks, dealer peeks for blackjack, blackjack pays 3:2 and always wins, player 21 always wins, double on any number of cards and any total, double after split, split to four hands, draw and double on split aces, double-down rescue, late surrender, and the standard bonus pay table with 5-card 21 at 3:2, 6-card 21 at 2:1, 7-or-more-card 21 at 3:1, and 6-7-8 or 7-7-7 at 3:2 mixed, 2:1 suited and 3:1 in spades.
Not priced here: re-doubling, the Super Bonus jackpot, the envy bonus, eight-deck shoes, and a 6:5 blackjack payout. The Super Bonus is a flat dollar amount rather than a multiple of your bet, so it is valued separately on the bonuses page. It adds roughly 0.03 percentage points at a minimum bet and less at any larger bet.
[TODO: price re-doubling, the eight-deck shoe, and a 6:5 blackjack payout through the same engine and add them to the rule table.]
Common questions
Why is the element of risk lower than the house edge?
The house edge is measured against the opening bet. The element of risk is measured against all the money that actually crosses the line, which averages 1.142 units per round once doubles and splits are counted. Same expected loss, larger denominator.
How much does bad play cost?
More than the rules do. Playing Spanish 21 with a blackjack chart gives back several tenths of a point on its own, and never rescuing gives back another 0.15. See common mistakes.
Are these numbers exact or simulated?
Simulated, and labeled as such. The dealer bust probabilities and the bonus deal probabilities are exact enumerations. The overall house edge is a Monte Carlo mean over 100,000,000 rounds with the confidence interval published beside it.