Blackjack odds: how 6:5, soft 17 & decks move the house edge

A sourced guide to where the casino’s advantage in blackjack comes from & which table rules make it larger or smaller.

How blackjack pays

According to the Wizard of Odds rules page, blackjack is played with one to eight 52-card decks. Aces count as 1 or 11 points, cards 2 to 9 count at face value, & tens & face cards count as ten.

A “blackjack”, also called a natural, is an ace plus any 10-point card on the first two cards. It outranks every other 21-point hand.

The Wizard of Odds says winning wagers pay even money, meaning the stake is matched, “except a winning player blackjack usually pays 3 to 2”. After the players have acted, the dealer turns over the face-down “hole card” & draws another card on 16 or less.

Some jurisdictions write the payouts into law. In Pennsylvania, 58 Pa. Code § 633a.13, as amended with effect from 11 January 2025, says the casino operator, called the “certificate holder”, pays winning wagers at 1 to 1, a blackjack at 3 to 2 & winning insurance wagers at 2 to 1.

Where the house edge comes from

The house edge is the average share of each bet the casino expects to keep over time. In blackjack it comes mostly from the order of play.

The player acts first. If the player goes over 21, or busts, the bet is lost at once, even if the dealer would also have bust. The Las Vegas Advisor says losing this “double bust” alone “gives the house an advantage of about 8%”.

The 3 to 2 bonus on naturals gives back about 2.3%, according to the same source. A player who copies the dealer, whatever the dealer’s visible card, therefore faces an edge of about 5.7%. The Wizard of Odds describes this “mimic the dealer” approach as always hitting 16 or less & standing on 17 or more, including a soft 17.

That figure has a long history. Baldwin, Cantey, Maisel & McDermott’s 1956 paper “The Optimum Strategy in Blackjack”, published in the Journal of the American Statistical Association, calculated a -5.6% expectation for this approach, & Ed Thorp later revised it to -5.73% in Beat the Dealer.

What basic strategy does

Basic strategy is the set of correct decisions for each player hand against each dealer card, based on the cards showing. The Las Vegas Advisor says it makes up most of the gap, with the gains coming, in order, from proper hitting & standing, doubling, splitting, & hitting soft 17 & 18, options the dealer does not have.

The right strategy depends on the table. The Wizard of Odds advises players wanting a strategy that is always correct to “use the appropriate basic strategy for the set of rules you are playing”.

Basic strategy lowers the edge but does not remove it. According to Casino.org, with perfect play players can expect to lose an average of 50 cents for every $100 wagered at 3:2 blackjack, & $1.40 at 6:5.

How the number of decks changes the edge

The Wizard of Odds calculated the edge by number of decks using rules it chose in 2020: dealer hits soft 17, blackjack pays 3 to 2, doubling allowed after splits, any pair including aces re-split up to three times, no surrender, & cards shuffled after every hand.

With basic strategy, it puts the house edge at 0.014% for one deck, 0.341% for two, 0.499% for four, 0.551% for six & 0.577% for eight. That is a gap of 0.563% between eight decks & one, & the site concludes that “the fewer the decks, the better the odds are for the recreational player”.

Part of the reason is card removal. In the Wizard of Odds analysis, a winning player blackjack happens 4.649% of the time with one deck against 4.527% with eight.

The Las Vegas Advisor measures rules against a benchmark single-deck game, which it calls 0.00%, where the dealer stands on soft 17 & blackjack pays 3-2. It says dealing from six decks instead of one costs the player 0.55%, & notes that figures differ slightly between sources because of calculation assumptions & rounding.

Dealer hits or stands on soft 17

A “soft” hand contains an ace that can still count as 1 or 11. The Wizard of Odds defines a soft 17 as the dealer holding “an ace and any number of cards totaling six points”, & says that at some tables the dealer will also hit it.

The Las Vegas Advisor says hitting soft 17 costs the player 0.21%. The effects are cumulative, so six decks plus a dealer who hits soft 17 move its 0.00% benchmark game to -0.76%.

The Wizard of Odds rule table, measured against standard US rules of eight decks with the dealer standing on soft 17, puts the same change at -0.22%.

3:2 or 6:5: the costliest rule

Casino.org says a $10 bet returns $15 for a natural at 3:2 but only $12 at 6:5, in each case on top of the original stake. That $3 difference “increases the house edge by nearly 1.4%”.

The Las Vegas Advisor calls 6-5 the rule with the biggest negative effect, at -1.36% on its own. A typical 6-5 single-deck game where the dealer hits soft 17 is -1.57% against basic strategy, which it describes as “two to three times worse than a standard 3-2 shoe game”. The Wizard of Odds table gives -1.39% for 6-5.

According to the Las Vegas Advisor, as cited by Casino.org, the Flamingo introduced 6:5 on its single-deck games in 1999. By 2010 it applied at 25% of Strip blackjack tables, especially lower-limit ones, & Casino.org describes it as now the standard at Strip tables.

Casino.org reports that Strip casinos still offering 3:2 typically do so at $25 to $50 minimums or only in high-limit salons. It also reported that the Strat had added 3:2 tables & that the Palms, on Valentine’s Day, eliminated all 6:5 payouts, while the Rio has offered both since reopening under new ownership in 2023.

Doubling, splitting & surrender

Doubling means doubling the bet in exchange for “one, and only one, more card”, the Wizard of Odds says. Splitting lets a player with a pair, or any two 10-point cards, add an equal bet & play two separate hands.

Usually a player may keep re-splitting up to four hands. Split aces get only one card each, an ace & ten after a split counts as 21 rather than blackjack, & some tables bar doubling after splitting or re-splitting aces.

The Las Vegas Advisor values unlimited splits at about +0.02% & re-splitting aces at +0.06%. In its example, adding both took a six-deck game at the Plaza from -0.63% to -0.55%.

Surrender means giving up half the bet & not playing the hand. The Wizard of Odds says it is only available on the first two cards & some casinos do not allow it at all.

Insurance & even money

According to a Wizard of Odds lesson by Michael Shackleford, insurance is offered when the dealer shows an ace. It is a side bet of up to half the original stake that the hole card is a 10-point card, paying 2 to 1 if it wins.

In a six-deck shoe, Shackleford counts 96 cards out of the remaining 311 that win the bet & 215 that lose it. The player can expect to lose 7.4% of whatever is staked on insurance, assuming no card counting.

When the player holds a blackjack against a dealer ace, the dealer may offer “even money”, a 1 to 1 payout before checking the hole card. Shackleford says this “is the same thing as taking insurance”: the player wins one unit either way, while declining returns an average of 103.88% of the bet at 3 to 2.

Losses, limits & self-exclusion

Even with perfect play, the standard games keep a house edge, so losses accumulate over time. Casino.org estimates that a $1,000 bankroll, played at 100 hands an hour with $10 bets, lasts about 2,000 hours at 3:2 but only 714 hours at 6:5.

The UK Gambling Commission describes self-exclusion as a tool for people who have recognised that their gambling is harmful to them. Its page, last updated on 27 March 2026, says GAMSTOP ONLINE lets people self-exclude from online operators with one request.

Once a self-exclusion agreement is made, the Commission says the business must close the account, return any money in it & remove the person’s details from its marketing databases. It adds: “In addition to self-exclusion, you should also seek support.”

Questions

What is the house edge in blackjack with basic strategy?

It depends on the rules. The Wizard of Odds puts it between 0.014% for one deck & 0.577% for eight under its 2020 baseline rules, & Casino.org says perfect play loses an average of 50 cents per $100 at 3:2.

How much worse is 6:5 than 3:2?

Casino.org says 6:5 adds nearly 1.4% to the house edge, & the Las Vegas Advisor puts it at 1.36%. On a $10 bet, a natural returns $12 instead of $15.

What does it cost when the dealer hits soft 17?

The Las Vegas Advisor says it costs the player 0.21%, & the Wizard of Odds rule table gives 0.22% against standard US eight-deck rules.

Is taking even money different from insurance?

No. Michael Shackleford of the Wizard of Odds says the even money offer is the same as taking insurance when holding a blackjack against a dealer ace.

What happens to an online account after self-exclusion in Great Britain?

According to the UK Gambling Commission, the gambling business must close the account & return any money in it. GAMSTOP ONLINE covers online operators with one request.

Sources

• lasvegasadvisor.com
• wizardofodds.com
• casino.org
• wizardofodds.com
• wizardofodds.com
• law.cornell.edu
• lasvegasadvisor.com
• gamblingcommission.gov.uk

Sources checked 31 October 2026. Information only. 18+.