I recently published a post about how slot machines really work, and I enjoyed writing it so much that I thought I’d write a companion post about how blackjack really works. I know enough about blackjack to know that most casual blackjack players are pretty confused about the nuts and bolts of how the game really works.

In my slot machine post, I mentioned that the first thing you needed to understand about slots is that they can’t be beaten in the long run. This is NOT true of blackjack.

In fact, blackjack is one of the few games in any casino which can be beaten by a skilled player. Counting cards is the best known way to get a long-term edge against the casino in blackjack, but it’s only one of multiple advantage play techniques that can earn you money over the long run.

Even if never learn any advantage play techniques, blackjack has one of the lowest mathematical edges in the house when compared to other games. It requires some memorization, but using basic strategy can get the edge of many blackjack games as low as 0.5%. That’s about as close to an even money contest as you’ll find in any casino.

Blackjack might not have as many myths and misconceptions as slots, but there’s still a lot of nonsense out there on the subject.

I hope this post will clear up a lot of that confusion.

Here’s how blackjack really works:

Dealers, Playing Cards, Points, and Totals

Blackjack is a casino card game that uses a standard deck of playing cards. Depending on which table you play at, multiple decks might be in use.

A standard deck of playing cards has 52 cards in it. These cards are divided into 13 ranks and 4 suits.

The cards are ranked ace, 2, 3, 4, 5, 6, 7, 8, 9, 10, jack, queen, and king.

You’ll find one card of each of these ranks in the following 4 suits: clubs, diamonds, hearts, and spades.

For the purposes of most blackjack game, the suit doesn’t matter, but it’s helpful to know how the deck works.

Blackjack is a comparing game of points. Each player competes with the dealer independent of the other players. (In a game like poker, you’re competing with the other players at the table. In blackjack, you only compete against the dealer.)

You start with a 2-card hand, and so does the dealer. Your goal is to get as close to 21 as possible without going over, which is how you beat the dealer. If you get a total of 22 or higher, you lose immediately. That’s called going “bust.”

The cards each have point values based on their rank. The numbered cards all have points equal to their rank. The 9 of hearts is worth 9 points. The 9 of spades is also worth 9 points.

The face cards—the jack, queen, and king—are each worth 10 points.

The ace can be counted as 1 point or 11 points, depending on what the other cards in your hand are like.

Most of the action of the game is based on whether you decide to stop taking additional cards. You decide this based on your total.

But the dealer also has a 2-card hand, and the dealer has one of those cards face-up, so you have information to help you decide what the right move to make is.

The house gets its edge in blackjack by making you complete the action on your hand before the dealer has to play his hand. If you go bust, you lose immediately. The dealer might go bust, too, but if you’ve already busted, the dealer still has your chips.

That’s the simplest way of understanding how the house can offer a game where the skilled player can make really good decisions.

In fact, the casino has to offer additional playing options besides taking cards or standing to keep the game competitive enough to play.

You have other options besides just hitting or standing. You can also:

  • Double down
  • Split
  • Surrender
  • Take insurance

Each of these options gives you a little more of a mathematical edge against the casino, although your overall edge is still negative.

What Decisions Do You Get to Make in Blackjack?

The most obvious decisions are whether to take an additional card or not. You can ask for another card by “hitting.” If you decide to just go with the total you have now, you’re “standing.”

Some of these decisions are obvious. For example, if you have a total of 19, you’ll stand. That’s so close to 21 to be hard to beat. It’s also extremely likely that you’ll bust if you take another call. The only 2 cards in the deck which can help you in this situation are the ace and the 2.

On the other hand, if you have a total of 9, you’ll obviously want to hit. It’s impossible to bust your hand with a total of 9, and you’ll always improve your hand by taking an extra card.

Your totals aren’t as cut and dried as all that, though. If you have an ace in your hand, you can count it as 1 point or as 11 points. In that case, you’re said to have a “soft hand.” You’re more likely to hit a soft hand, because it’s harder to bust a soft total.

On the other hand, if you have a hand with no aces—or a hand where the ace must be counted as 1 point to avoid busting—you’re said to have a “hard hand.” You’ll play such hands more conservatively, being more likely to stand with them.

Other totals are less obvious how to play appropriately, too, by the way. A hard total of 16 has a high probability of busting if you hit it, but it also has a high probability of losing if you don’t hit it.

If you’re a basic strategy player—and I’ll describe basic strategy in detail soon—you’ll account for what card the dealer has showing. If the dealer has a 3, 4, or 5 showing, you’ll usually play less aggressively (be more likely to stand). But if the dealer has a 7 or higher showing, you’ll usually play more aggressively (be more likely to hit).

Also, if you have a 2-card total of 21, that’s considered a “natural” or a “blackjack.” Most casinos pay off at 3 to 2 for a natural, although some games only pay off at 6 to 5. (More about that later.)

Those aren’t the only options, though. The first of the other options you have is to “split.” You can only split your hand if you’re dealt 2 cards of the same rank.

When you split your hand, you put up a 2nd bet, the same size as your original bet. You then start 2 hands, with one of the cards you have now as the starting card for each of those 2 hands.

If you have 2 aces, for example, splitting is obviously a good move. Since an ace is worth 11 points, if you’re dealt a 10 for your new 2nd card in each hand, you’ll have a total of 21 for each hand. (And there are more cards in the deck worth 10 points than you might think—16 of them, in fact.)

“Doubling down” is another option you can usually use on any total. When you double down, you put up an additional bet (in effect, “doubling” the size of your bet) in exchange for taking one (and exactly one) more card. This makes sense when you have a total of 11, because the probability of getting a 10 is really good.

“Surrendering” is when you have such a lousy hand that you’d just rather get out of it. To surrender, you forfeit half your bet, but you give up your hand. It’s comparable to folding in poker. Most situations don’t warrant surrendering, but it can be a useful option sometimes. Not all games offer the option, and some casinos offer it at different times—before or after the dealer checks for blackjack.

“Taking insurance” is an optional side bet you can take when the dealer has an ace showing. It’s a bet that the dealer has a blackjack. (If the dealer has a blackjack, all the players automatically lose immediately, unless they also have a blackjack.) It’s a sucker bet, unless you’re counting cards.

The House Edge in Blackjack and Its Effects on Your Bankroll

The house edge in blackjack varies based on the rules variations in effect at the casino and at the table where you’re playing. In blackjack, the dealer must play his card per a certain set of instructions, regardless of what the players’ cards are.

The dealer always must hit a hand with a total of 16 or less. The dealer must stand on a hand with a total of 17 or more, with one exception:

In some casinos, a dealer with a “soft 17”—a total of 17 that includes an ace, hits instead of standing. It’s better for the player if the dealer stands on soft 17. This is one example of a rule that affects the game’s mathematical edge.

The house edge, by the way, is just a way to measure the casino’s mathematical advantage over the player. It’s expressed as a percentage, and it’s the amount of each bet that the casino expects to win in the long run, on average.

That last part—in the long run, on average—is important.

It is, in fact, impossible to lose the amount of the house edge in the short run in blackjack. The house edge usually ranges between 0.5% and 1%.

That might warrant further explanation.

If you place a $100 bet on a blackjack hand, it’s impossible to lose just 50 cents or $1. You’ll win or lose $100 most of the time. You might win $150 if you hit a natural. You might win or lose $200 if you split or double down.

The house edge is an average over a HUGE number of hands. It’s a mathematical prediction. In the long run, thousands and tens of thousands of hands, you’ll come close to seeing it realized.

But you should also keep in mind that when gambling writers talk about the house edge in blackjack, they’re using a number that assumes you’re playing every hand according to perfect basic strategy.

And that’s what I want to talk about next.

How Blackjack Basic Strategy Works

In any given situation in blackjack—and there are fewer possible situations than you probably think—only one play is mathematically optimal. That’s the play with the highest expected value.

With some hands, you’re stuck with a dud. The highest expected value is still negative.

With other hand, you’re going to do well no matter what. Your goal is to win as much money as possible.

You have 2 pieces of information with every blackjack hand:

  • Your total
  • The dealer’s face up card

The mathematically correct play in every situation is a function of those 2 pieces of data.

For example, if you have a hard total of 13, and the dealer is showing a 3, the correct move is to stand.

A lot of players might hit a hand with a total of 13, as any card of 8 or less is going to improve your hand without busting it.

But if the dealer has a 3 showing, he has a higher than usual probability of busting. You’re better off standing pat and waiting for him to bust. Don’t risk busting your own hand first.

On the other hand, if you have a soft 13 in that same situation, you’ll hit. It’s impossible to bust that hand because you cannot possibly get anything that will make your total 22 or higher. You can change the value of that ace from 11 to 1 to stay in the game. So it’s mostly upside.

The dealer only has 10 possible up cards. You only have 26 different totals to worry about. So a basic strategy chart only has 260 decision points.

But many hands are played the same in certain situations, so you don’t have to memorize 260 different rules for basic strategy. For example, you’ll always split aces and 8s, but you’ll never split 4s, 5s, or 10s.

Here’s another example:

If you have a hard 16, you’ll stand if the dealer has a 6 or less, but you’ll hit if the dealer has a 7 or more. That covers 10 possible situations you’ll face with a hard 16, but the strategy for that hand only requires you to memorize 2 situations.

Many players don’t use basic strategy. Others think they’re using basic strategy when they’re not. Still others will use basic strategy part of the time, but they’ll deviate when they have a hunch.

Here’s the truth:

Any deviation you make from basic strategy in blackjack hurts your return. It makes the house edge higher, not lower.

You don’t want that.

I discussed in the post about slot machines the effect that the house edge combined with your rate of play and average bet size has upon your results over time. Blackjack is easily illustrated, too:

I’ll assume you’re playing at a table with a couple of other people, so you’ll be seeing 70 hands per hour. I’ll also assume that you’re a classic low roller, playing for $5 per hand. You’re putting $350 into action every hour.

If you’re facing a house edge of 1%, you’re looking at an expected hourly loss of $3.50. If you’re playing in a game with good rules variations and a house edge of 0.5%, the cost of your blackjack entertainment got even lower—it’s now $1.75 per hour.

But if you ignore basic strategy, the house edge probably goes up to at least 4%–maybe even 5% depending on how poorly you play each hand.

Now you’re looking at expected hourly losses of $14 to $17 per hour.

There’s really no reason to ignore basic strategy or to not follow it. Heck, if you absolutely cannot memorize it, you can buy a plastic card in the gift shop of any hotel/casino with a color-coded table showing the correct basic strategy for every situation.

The Truth about Counting Cards and Other Advantage Techniques

I remember giggling a little bit the first time I saw Vegas Vacation during the part where Chevy Chase is explaining to his son that blackjack is the only game where you can get an edge against the house by being skillful. The implication was that all you needed to do to get an edge was use perfect basic strategy.

If you faced the right rules variations, that might be true.

But most casinos don’t have the right rules variations in place.

If you want to get an edge over the casino, you must learn how to count cards. Luckily, counting cards is so much easier than you ever thought possible.

First, it’s not like Rain Man, where Dustin Hoffman memorized every card that had been dealt and knew exactly what card was coming next.

Card counting works because a deck’s composition changes based on the cards that have already been dealt. Since the cards are randomized (shuffled), you’ll sometimes wind up with a deck which has a different ratio of high cards to low cards.

And remember how I mentioned that a 2-card total of 21 pays off at 3 to 2? This is more likely to happen if the deck has more aces and 10s in it than normal.

What card counters do is track (in a rough way) the ratio of high cards to low cards by assigning a value to low cards and another value to high cards. This helps them estimate how favorable the deck is.

When the deck is favorable enough, a card counter raises the size of his bets to take advantage of that greater probability of getting a 3 to 2 payoff.

Skilled card counters also know how to change their basic strategy decisions based on the count. For example, if there are enough 10s in the deck relative to the lower cards, taking insurance might change from a sucker bet to a positive expectation bet.

Card counting isn’t cheating. It isn’t illegal, either. Casinos just hate it, though.

Think about it, for a minute. Why would it be illegal to think about a game while you’re playing it? Can the government really outlaw thinking about a game and its odds while playing?

On the other hand, if you’re using some kind of device to keep up with the count, you ARE cheating. In Nevada, that’s a felony. Luckily, it’s not necessary. Most reasonably intelligent people can learn to count cards if they’re willing to put in the effort required.


That’s how blackjack really works. It’s a simple enough game, really, and the house gets most of its edge from letting the players act first. If you and the dealer acted simultaneously, like you do during a showdown in poker, the game would be 50/50.

But you can cut the house edge in blackjack to a tiny amount just by memorizing and using basic strategy.

You can even get an edge over the casino by learning to count cards, which is neither illegal nor immoral.

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