BlackjackInfo Blog

Why Does The Number of Decks Matter in Blackjack?

Fewer Decks are Better. Do You Know Why?

When it comes to the number of decks in a blackjack game, the fewer the better. Most players have heard this fact somewhere along the line, but many of them don’t know why fewer is better.

I often get this question by email, where players will note that the proportion of each rank of card is the same whether the casino uses a single deck or shuffles six decks together. Regardless of how many decks are in play, we start out with one thirteenth of the cards being Aces.

You Get More Blackjacks in Games With Fewer Decks

Despite the initial card proportions being equal, in games with fewer decks you will be dealt more blackjacks. You will also be more successful in your double downs. How can that be, when all the ranks are equally represented no matter how many decks are used? It is because removing cards has more impact in a game with fewer decks.

How Often Will You Draw a Blackjack From a Single Deck?

To get the probability of drawing a blackjack from a single deck, we multiply the chance of drawing an Ace by the chance of drawing a ten-value card. In a single deck of 52 cards there are 4 Aces and 16 ten-valued cards (4 each of Ten, Jack, Queen, and King).

p(Ace) = 4/52 = 1/13
p(Ten) = 16/51

Note that the second line reduces the number of cards in the divisor to 51, to account for the removed Ace. And that’s where the difference lies.

We also need to double the result since we could draw either (Ace,Ten) or (Ten,Ace). Our final result is:
p(Blackjack) = p(Ace) * p(Ten) * 2 = (1/13) * (16/51) * 2 = 4.83%

The probability of drawing a blackjack from a single deck is 4.83%.

How Often Will You Draw a Blackjack From Two Decks

Same idea with two decks, with different numbers. 104 total cards, including 8 Aces and 32 ten-value cards…

p(Blackjack) = 8/104 * 32/103 * 2 = 4.78%.

The probability of drawing a blackjack from two decks is 4.78%.

More decks means slightly fewer blackjacks. In six decks, the probability drops further yet to 4.75%.

Double Downs Work Better in Fewer Decks Too

The same effect impacts double downs. If you double your initial hand of (6,5) for a total of 11, then you are slightly more likely to draw a face card to make 21 if the game uses fewer decks.

Astute readers may notice that the dealer gets the benefit of these changes as well. That’s right, the dealer gets more blackjacks in single deck, and the dealer draws to 21 more often just like the player. But note that a player wins 3:2 for blackjack, while the dealer gets only even money. And for hands like the double down example, the player wins twice the initial bet. So while both player and dealer get more of these good hands, the player is rewarded more handsomely for his.

But You Get Fewer Pat 20s in Fewer Decks!

It’s not all good news with less decks. For the same reason, you will get fewer dealt hands of 20! Once you remove the first ten-value card, there are only 15 tens left in 51 cards in single deck, while in double deck your chances are better with 31 out of 103.

This impact of fewer pat 20s affects players and dealers equally, so it’s really a wash.

The bottom line is that, all other things being equal, you should play in games with fewer decks. Just make sure they pay 3:2 on blackjack!

The State of Blackjack – Opportunity Amidst the Apocalypse?

A Tale of Two Cities
Charles Dickens may as well have been describing recent developments in casino blackjack…

“It was the best of times, it was the worst of times.”

Rules and conditions at casino blackjack tables have been steadily declining for years, and there are a lot of really bad games out there.

6:5 Has Spread Far and Wide

I just tallied up the games offered in Las Vegas, based on the latest issue of Current Blackjack News. A depressing 40% of the regular blackjack tables in Las Vegas now pay only 6:5 for blackjack.

A New Design, and a New Knowledge Base

For the last few months, I have been busily working on the new design at BlackjackInfo. And finally, it’s ready to go, so you are looking at the result.

The biggest enhancement is that the site now adapts to whatever device you are viewing on, so check it out on your tablet or mobile phone, including landscape and portrait mode.

All of the site’s most popular features are still here, including the Strategy Engine, and a complete rewrite of the Blackjack Rules explanation.

ThePOGG Posts an Interview with Ken Smith

Have you heard of ThePOGGThePOGG? ThePOGG is “The Player’s Online Gambling Guide”, a site created by an experienced online casino player who does casino reviews and dispute resolution for online gamblers.

This week, the site’s creator posted an interview with me.  Among the wide-ranging topics are a story about how I was actually too lucky at one promo, a back story of how randomly generated literature eventually led to my interest in gambling, and other tales from a life at the tables. I hope that BlackjackInfo visitors will find it interesting.

See the full interview here: ThePOGG Interviews Ken Smith

Ken Smith on Gambling With an Edge Podcast

Gambling with an Edge

Earlier this year, I was the guest on the Gambling With an Edge radio show in Las Vegas. I mentioned it in the BlackjackInfo email newsletter, but I just realized that it never got posted here on the blog.

The show includes a couple of stories that I think BlackjackInfo visitors will find interesting. I describe one play where I won over $100,000 on a single hand of cards, and another play at a 2:1 blackjack promotion that yielded a big profit along with an uncomfortable situation.

You can listen to the show, and see more details at Gambling With an Edge.

Learning Card Counting Indexes? Don’t Make This Mistake

Index Numbers

Once you have basic strategy committed to memory, and you have learned to count cards and vary your bet, the next step in fine-tuning your game is to add strategy variations using index numbers.

When I first began to learn about strategy variations, I found them confusing.  Based on the number of emails I get on the topic, I know that I am not the only one.

I was especially confused about the way indexes are presented.  I thought I could see a better way.  But eventually I switched to the standard method, and it definitely has its benefits.

Blackjack Player Sues After Losing $500,000 While Drunk


For players, free drinks are an important part of the casino experience. For casinos, serving free cocktails generates a nice return on investment.

This week, a 52 year old California man filed suit against the Downtown Grand Casino in Las Vegas, alleging that the casino continued serving him drinks and extending gambling credit to him after he was obviously intoxicated. He went on to sign markers for $500,000 and lost it all, not realizing how much he had lost until he awoke the following day.

Double Down on a 6:5 Blackjack? Read This First…

Bad Choice

The plague of 6:5 blackjack has been well documented here. (See 6 to 5 Blackjack? Just say No! and The Casino Floor as a Minefield.)

If you have any other game choices available, you should not be playing a game that pays only 6:5 on blackjack.

Yet some players do play these games. Don’t worry, I’m not going to chastise you if you sometimes play these games. But I do want to make sure that you are not making a bad game even worse…

16vT: RS WTF?!


Forgive the cryptic title. I couldn’t resist.  So, what does it mean?  16vT is shorthand for the player hand of sixteen against a dealer upcard of Ten.   “RS” is a strategy abbreviation.  “R” means SuRRender, and “S” means Stand.  So, “RS” means Surrender if you can, otherwise Stand.

And of course, WTF is an abbreviation of the message I often get via email when someone thinks they have found a mistake in the strategy provided by my Blackjack Basic Strategy Engine.