Posts Tagged ‘blackjack odds’

Blackjack odds: Will dealer bust with a 5 or 6 up card?

Monday, August 30th, 2010

Anyone schooled on blackjack basic strategy breathes a sigh of relief when they see the dealer draw a five or six as an up card. They know those are the worst dealer hands and they feel they have a good chance of winning. Players who don’t understand the blackjack odds, though, might assume that the dealer will bust and they will win. The truth is, that will happen less than half of the time.

The correct strategy against a dealer five or six up card is to stand if you have a 12 or higher, but that doesn’t guarantee success. Players look at the dealer up card and assume that they have a 15 or 16, given the fact that there are more ten cards in a deck than any other. However, there are only 4/13 odds of the dealer having a ten in the hole.

If the dealer has a 5 as an up card, there is a 4/13 chance that he has a hand of 15 because four cards (ten, jack, queen, king) give him that total. The dealer has a 7/13 chance of having any kind of stiff hand, which is a hand of 12-16. All stiff hands have good chances of busting, but your odds might not be as good as you think.

If the dealer has a five as an up card, he has a 41.8% chance of busting. He has a 12.2% chance of finishing with a hand total of 17, an identical chance of drawing an 18, an 11.8% chance of drawing a hand of 19, an 11.2% chance of finishing with a hand of 20 and a 10.8% chance of finishing with a hand of 21.

If the dealer has a six as an up card, he has a 42.3% chance of busting. He has a 16.6% chance of drawing a 17, a 10.6% chance of drawing an 18 or 19, a 10.2% chance of drawing a 20 and a 9.7% chance of drawing a 21.

What that means is if you have a hand of 12 and stand against a dealer 5 up card, you only have a 41.8% chance of winning the hand, because if the dealer finishes with any of those other totals, you lose. However, standing in that situation is still the best strategy because the risk of you busting if you take a hit.

Understanding the odds leads to making better decisions and getting more enjoyment out of the game of blackjack. Too many players get upset when they lose against a dealer five or six because they take a win for granted in that situation. Though your odds are good, they aren’t as good as most people think.

Blackjack odds: Drawing a natural blackjack

Tuesday, August 10th, 2010

A natural blackjack is the best hand in the game. Players search for those ace-ten combinations. They love the prospect of a 3:2 payout and a guaranteed win (unless the dealer also has a natural blackjack). It’s the reason card counters keep track of the number of tens that have been played. It’s the reason we get excited by getting dealt an ace and worried when the dealer shows an ace. But how likely are you to draw a natural blackjack?

The likelihood of drawing a natural blackjack depends on the number of decks in play. Assuming an infinite number of decks, you or the dealer have a 4.73% chance of drawing a natural blackjack, which is once every 21 hands. If you’re worried about your blackjack being spoiled by the dealer also drawing a blackjack, which would lead to a push, that only happens 0.22% of the time, or once out of 450 hands.

If you or the dealer already have an ace, there is a 30.77% chance – or four out of 13 – of turning it into a natural blackjack. If you or the dealer already have a ten, there is a 7.69% chance – one out of 13 – of turning it into a blackjack.

The chances of these events happening whether at an online casino or land-based differs depending on the number of decks. In an eight-deck game, which is the most common at casino blackjack tables, there is a slightly higher chance of drawing a natural blackjack: 4.745%. In a six-deck blackjack game, you have a 4.749% chance of drawing a natural blackjack. There is a 4.756% chance of getting a blackjack in a four-deck game and in a single-deck game, the odds are raised to 4.83%. As you might have noticed, the odds increase as the number of decks decrease.

It is good to keep in mind the odds of drawing a blackjack, particularly when either you or the dealer have an ace or a ten card. Knowing your odds is key to successfully executing blackjack basic strategy.

Blackjack strategy: playing the dealer

Thursday, July 8th, 2010

Today I read a blackjack “tip” from a supposed gambling expert. That expert said that you should “aim to get closer to 21, not to beat the dealer.” I was shocked, since this is exactly the opposite of what I advise.

In the game of blackjack, the goal is not to get as close as you can to 21, though that is sometimes what people say. The goal is to beat the dealer. Whether you beat the dealer with a hand of 20 or a hand of 4, you get the same reward. Sure, most of the time you want to get close to 21 because the dealer is going to hit until he gets to 17 or better. However, people who follow a strategy of trying to get close to 21 often play too aggressively and hit when they should stand.

Playing to get closer to 21 ignores the chance of the dealer busting. If the dealer busts, you win with any hand, as long as you don’t bust as well. For example, if you have a hand of 12, that’s not very close to 21. Therefore, people following a “get as close to 21 as possible” strategy would take a hit regardless of the dealer’s hand. However, if the dealer has a hand of 4, 5 or 6, blackjack basic strategy says to stand.

You would stand on those hands because the dealer is likely to have a stiff hand, which is a hand between 12 and 16. With those hands, the person is likely to bust if taking a hit. Since you also have a stiff hand, taking a hit is risky. In this case, it’s best to stand and hope that the dealer busts. How likely is he to bust? Let’s break them down.

If the dealer has a hand of 14, there are five cards (3, 4, 5, 6, 7) he can draw that would beat your hand. The dealer can draw two cards (ace, 2) that would leave him with another stiff hand. There are six cards (8, 9, 10, J, Q, K) that would bust his hand. Therefore, if the dealer has a 14, there is a 8/13 chance that the card he draws will be bad for him and good for you.

Now let’s look at if the dealer has a hand of 16. Here your odds are even worse. There are only five cards (ace, 2, 3, 4, 5) that will help his hand and the other eight cards (6, 7, 8, 9, 10, J, Q, K) will bust him. Combine that with the fact that, with a 12, you have a stiff hand, you can see that the odds are best to stand and hope the dealer busts.

For that reason, you should ignore any advise that says you should get as close to 21 as possible. While that is part of the strategy, it is secondary to beating the dealer. Often, getting as close to 21 as you can gives you the best chance of beating the dealer, but that is not always the case.

As always, this strategy works in online casinos as well as in the brick and mortar variety.

Blackjack Strategy: Dealer 8 Card

Tuesday, June 8th, 2010

Reducing the house edge in blackjack to an acceptable level – as low as 0.5% — requires strict adherence to blackjack basic strategy. This strategy works in online casinos as well as the brick and mortar variety. Given the importance of basic strategy, I decided to analyze it from many different angles. Here is the basic strategy for when the dealer shows an 8 as the up card.

If the dealer shows an 8 as an up card, he has a good chance of having a hand of 18, given the high number of 10-value cards in the deck. That makes this situation drastically different from when the dealer shows a 2-6, because that leaves the dealer with a high likelihood of a stiff hand. If the dealer has an 18, he will stand and there is no chance of the dealer busting.
First of all, as always, you should hit if you have an 8 or less, because there is no risk of busting and your cards aren’t good. If the dealer shows an 8, you should also hit if you have a 9. Again, there is no risk of busting, but your hand isn’t really good enough to double down.

If you have a 10 or 11, you should double down against a dealer 8. That is because you have a good hand. Upon drawing the next card, you have a good chance of drawing a 20 or 21, which are tough to beat. Given the strength of those potential hands, you should double the money on your bet.

If you have a hard 12-16, you should hit against a dealer 8 up card. Unfortunately, you have a stiff hand, which is likely to bust but is too low to outdraw the dealer. In fact, you can only win if the dealer busts. When the dealer has an 8 as an up card, he is not likely to bust, since the dealer will stand on a 17 or better. For that reason, your odds are slightly better (though still not good) taking a hit than standing.

If you have a hard 17 or better, you should always stand, no matter what card the dealer shows. There are too many cards that will bust you and not enough that will improve your hand.

For soft hands, you should hit if you have a soft 13-17 against a dealer 8 up card. That is because, again, the dealer is unlikely to bust, so a hand below 17 is unlikely to win. For that reason, and because there is no risk of busting with a soft hand, you should take a hit and hope to improve your hand.

If you have a soft 18 or better, you should stand against a dealer 8 up card. If the dealer has an 18, you would tie with an 18 and win with a better hand, so there is no reason to risking drawing a card that reduces the value of your hand.

When it comes to splitting pairs, you want to do so conservatively against a dealer 8 up card. That is because the dealer likely has a good hand, so you want to be careful about doubling your bet. Therefore, if you have a pair of twos, threes or fours, you should take a hit. Splitting the pairs might not help your hands and doubles your bet against a good dealer hand.

If you have a pair of fives against a dealer 8 up card, you should double down. Despite the dealer’s good hand, you probably have a better one. Drawing one more card can give you a 20, which can only be bested by a hand of 21. Therefore, doubling the money on this hand is a good idea.

You should hit a pair of sixes and sevens against a dealer 8 up card, because splitting could give you two hands of 16 and 17, which could very well be outdrawn by the dealer’s hand. Therefore, you don’t want to double the bet.

You should split, however, if you have a pair of eights or nines. This splits up a hand of 16 (a stiff hand) or 18 and gives you a good chance of drawing two hands of 18 or 19. Given how bad a 16 is and how good hands of 18 and 19 are, combined with the fact that the dealer likely has an 18, this is the wise play.

You should never split a pair of tens, because you already have a hand of 20, and you should always split a pair of aces, since aces are the most powerful card in blackjack. They are the best because you can’t bust with a soft hand and you can use an ace to draw a natural blackjack, which pays 3:2.

The above strategy works in online casinos as well as the brick and mortar variety.

Blackjack Strategy: Dealer 3 Card

Thursday, May 20th, 2010

This is the second part in the series on basic strategy that covers what to do based on the dealer’s up card. In this post, we’re looking at when the dealer shows a 3.

If the dealer shows a 3, basic strategy says that he likely has a stiff hand (12-16) due to the likelihood of having a 10 in the hole. For that reason, you should stand if you have a hard 13-16, because those are also stiff hands that have a high probability of busting. If you both bust, you lose, but if only the dealer busts, you win no matter what cards you have.

Therefore, in this situation, it is best to stand pat. If you have a hard 17 or better, you should stand because those are good cards with a low chance of improvement, so you always stand with those hands.

If you have an 8 or lower, you should always hit because there is no risk of busting but your hand isn’t necessarily good enough to win by taking one more card. Therefore, you don’t want o double down. You should also take a hit if you have a 12 versus a dealer 3 up card, because even though it’s a stiff hand, it’s a stiff hand that will only bust if you draw a 10 card, meaning you have a 69% chance of improving your hand. And if the dealer doesn’t bust, your 12 loses.

If you have a hard 9, 10 or 11, you should double down when the dealer has a 3 as an up card. This is because the dealer’s hand is not good (probably a stiff hand) and your cards are awesome. Taking into account your high probability of drawing a 10 card, you have a good chance of having a 19, 20 or 21 when taking one more card. For that reason, combined with the dealer’s likelihood of busting, it is best to double your bet and take one more card.

Now for the soft hands. If you have a soft 13-16, you should take a hit. Unlike with a hard 13-16, there is no risk of busting, so it is a good opportunity to improve your hand without any risk.

If you have a soft 17 or 18, you should double down. Why? Let’s look at the possibilities. If you have a soft 17 (ace, 6), then 4 cards (ace, 2, 3, 4) improve your hand, 5 cards (5, 6, 7, 8, 9) give you a stiff hand, and 4 cards (10, J, Q, K) put you right back where you started: with a hand of 17. That means 62% of the cards will either help you or keep your hand the same while 38% will make your hand worse, but there aren’t any cards that can bust you. Therefore, it’s best to take a chance. You should stand on a soft 19 or better, though, because there aren’t many cards that can help you and you already have a great hand.

Now, let’s talk about the blackjack basic strategy for splitting pairs against a dealer 3 up card. If you have a pair of twos or threes, you should only split if you are allowed to double afterward. If not, take a hit. You should also take a hit with a pair of fours, because you don’t want to start two hands with a four, which are likely to lead to stiff hands. If you have a pair of fives, you should double down, because if you draw a 10 with the next card, you will have a hand of 20, which can only be bested by a dealer 21.

If you have a pair of sixes, sevens, eights or nines, you should split against a dealer 3 up card. A pair of sixes, sevens and eights unsplit are stiff hands (12, 14, 16), whereas if you split them you could end up with hands of 16, 17 and 18. You have better odds with those hands. A hand of 18 is good and hard to pass up, but the odds say you are better off splitting that pair of nines and hoping to draw 2 hands of 19.

As for the other two hands, no matter what card the dealer has, you should never, ever split a pair of tens. That is a hand of 20, which can only be beaten by a 21. I know you think you can split it and get 2 hands of 20, but the risk outweighs the reward when you already have a 20. As for a pair of aces, you always split that, no matter what card the dealer has. An ace is the most powerful card in blackjack, so starting 2 hands with an ace really increases your odds. Which would you rather, a hand of 12, which is a stiff hand, or two soft hands? Always split a pair of aces.

Blackjack Strategy: Dealer 2 Card

Wednesday, May 19th, 2010

I have covered blackjack basic strategy in a number of ways. I have written series on what to do with each soft hand, what to do with each pair, when to surrender and more. Now I am starting a new series for teaching basic strategy. I am doing this because I am bored and need something to write about.

Just kidding. Different people learn different ways and since blackjack basic strategy is so important to learn, I want to cover it from every angle. In this series, of which this is the first part, I will cover strategy from the point of view of the dealer’s up card. Based on what card the dealer shows when you are dealt your first cards, I will analyze what to do. Since we will go in order, the first in the series is a dealer 2.

If the dealer shows a 2, basic strategy takes into account the high probability of the dealer having a 12 (since there are more ten-value cards than any other value). Though a 12 is a stiff hand, it is the best of stiff hands (for the person with that hand). If the dealer has a 12, he has a 31% of busting on the next card upon taking a hit. In fact, statistics show that over 35% of the time, the dealer will bust when he has a 2 as the up card, even taking into account the times when the hole card is not a ten. All of that plays into your decision.

If the dealer shows a 2, you should stand if you have a 13-16. Obviously, you always stand with a hard 17-20. You stand with a hard 12-16 because you have a good chance (39%-62%) of busting if you take a hit, so it is best to stand pat and hope the dealer busts.

If you have a 10 or 11, you should double down because of the good chance of drawing a 10 with your next card, which would give you a 20 or 21. Even if you get a lesser card, though, you are likely to have a hand that beats the dealer’s 2.

If you have an 8 or 9, you hit because you have low cards and no chance of busting. If you have a 12, that is a stiff hand, but one with only a 31% chance of busting. It is better to try to improve your hand here, since only a 10 card will bust you.

If you have a soft 13-17, you should take a hit because you can’t bust. If you draw something that would cause you to bust, that simply makes your ace a 1 and gives you a hard hand. With a soft 18 or better, though, you already have a good enough hand that you are more likely to make it worse than better by taking a hit. For that reason, you would stand with a soft 18 or better.

When it comes to pairs, if the dealer shows a 2 you should always split a pair of sevens, eights, nines and aces. Each of those are solids hands to start with. If you have a pair of twos, threes or sixes, you only split if you are allowed to double afterwards. If not, you should take a hit. You should also hit a pair of fours, since one hand of 8 is better than a pair of potential stiff hands with fours. If you have a pair of fives, you should double down, since your next card has a good chance of giving you a 20. If you have a pair of tens, you already have a hand of 20, so you should always stand.

Want bad odds? Play the lottery

Monday, May 17th, 2010

I like playing blackjack. I think it’s a fun game and I play it in the hopes of winning money, but knowing that I am more likely to lose money. I am okay with that. However, some people give me a hard time about it, saying that gambling is “throwing money away” and that it’s a “waste of money.”

The first question I normally counter with is, “Don’t most hobbies cost money? Doesn’t a night out normally cost something?” Even if I lose money at the blackjack table, I am always responsible with my bankroll, so I never lose a large amount. Therefore, when I lose I simply consider it the cost of a fun night. Going to Disney isn’t cheap, either. Neither is going to a movie or baseball game. However, I never hear people talk about those activities as throwing your money away. Why? At least when I play blackjack I have a chance to break even or sometimes even make money. I guarantee you that you will never make money by taking the family to Disney.

Maybe people see it differently because gambling can cause you to lose lots of money, much more than you would lose doing most activities. It’s true that some people have lost their house, car and more by gambling their money away. However, doesn’t that come down to personal responsibility? You can blow a lot of money at Disney, too, if you decide to buy stuff at the souvenir shop, pay for a nice, sit-down meal instead of hot dogs, and stay in the resort overnight. If you can’t afford to spend all of that money, you need to have the responsibility to say no.

Being responsible with your money is just as possible in a casino. You may not be able to control whether you win or lose money on a hand (though you do have some control, luck is involved as well), but you can control how much money you bet. If you are responsible when playing blackjack, you should never lose a lot of money. I always plan how much money I will bet ahead of time and set that aside, not increasing my bankroll no matter what happens in the casino. Yes, folks, being fiscally responsible is possible when playing blackjack (even online blackjack).

Some people still won’t see my side of the argument and are simply against blackjack because it is gambling. Usually at that point I ask if they play the lottery. The answer is yes more often than you might think.

It is absurd to be against gambling while playing in the state lottery (and that includes the governments). After all, the lottery has the worst odds of all. In most 6-ball state lotteries, the chances of winning the jackpot are between 1 in 14 million and 1 in 16 million. Doesn’t sound too good, does it? Some people try to increase their odds by buying many lottery tickets at a time (which would be “throwing their money away”). How well does that work? Well, if you buy 50 lottery tickets every week, the odds say you will win the jackpot approximately once every 5,000 years. Most people don’t live that long.

Okay, so we know that hitting the jackpot isn’t likely with the lottery, but you can win smaller amounts of money, too. You might be wondering what the house edge is for the lottery. It’s 50%. Of all of the money paid into the lottery for the tickets, only half of it is ever paid out. The rest is used for other purposes. That is half of the money gone right away and you’re still going against all of the other ticket-buyers for the other half. To put things in perspective, double-zero roulette has a house edge of 5.26% and baccarat has a 1.24% house edge on bets on the player. Blackjack has even better odds. You can reduce the house edge to 0.5% if you follow perfect basic strategy. So which game would you rather play, the one with a 0.5% house edge or the game with the 50% house edge?

Blackjack Strategy: Don’t Take Insurance

Friday, April 30th, 2010

In the game of blackjack, whether you’re playing online blackjack or at a brick and mortar casino, you and the house have the same goal. That goal is to make money. Unfortunately, those goals are mutually exclusive. They can’t both occur at the same time. If you win money, the casino loses money and vice versa. For that reason, you need to keep in mind that while the dealer should be trusted, his interests are not the same as your own.

There are a lot of rules and decisions that are beneficial to the player, such as splitting and doubling in the correct situations. Unless you ask for help, though, the dealer won’t remind you to do that. The dealer probably won’t say, “You have a pair of sevens. Would you like to split them?” It’s up to you to know that you should split a pair of sevens.

However, there is one decision that the dealer will always ask you about and that is insurance. If the dealer has an ace as an up card, he will ask if you want to buy insurance against a blackjack. Not only that, but “Insurance pays 2 to 1” can usually be found printed right on the blackjack table, just to remind you. Is that out of the kindness of his heart? Hardly. The dealer is quick to ask about this because insurance is a bet with a high house edge. You’ll notice that the table doesn’t have “You should always split aces” printed on it.

Insurance is a suckers bet and you shouldn’t take it. For those who don’t know much about the rule, insurance is offered when the dealer has an ace as an up card, because in that case if he has a 10 in the hole, he has a natural blackjack and you would always lose unless you also have a blackjack. The dealer then offers insurance where you get paid 2 to 1 if he does have a blackjack and if he doesn’t, he wins that side bet and can also win the original bet if he still beats your hand.

Therefore, insurance is basically a bet that the dealer has a 10 in the hole. While there are more cards with a value of 10 than any other value, you need to remember that it’s still outnumbered. There are 4 cards (10, J, Q, K) out of every 13 that have a value of 10. That means there are 9 cards out of 13 that have a different value. In that case, the dealer would have a 69% chance of having something other than a 10 in the hole and a 69% chance of winning the insurance side bet.

For that reason, you shouldn’t take insurance when it is offered to you. In fact, as a general rule you should avoid any side bets in blackjack, because almost all of them have a higher house edge than the regular game. The only exception is if you are counting cards, which you can’t do at an online casino, and determined that the deck is rich in tens. In all other situations, if the dealer offers you insurance, say thanks, but no thanks.

Standard Deviation in Blackjack

Tuesday, April 27th, 2010

As has been discussed many times, blackjack has one of the lowest house edges in the casino and by using perfect blackjack basic strategy, you can lower the house edge to 0.5%. That means that in the long run, you can expect the house to take 0.5% of your money. But that’s not always what happens, is it? Sometimes you win more and sometimes you lose more. Anything that deviates from the average of a 0.5% house edge is called “variance” and you calculate variance using “standard deviation.”

If you think back to math class, you’ll remember that probability can be charted with a bell curve. On that curve, the middle amount is the average. Using that bell curve, you can show the normal distribution, which is the probability of possible outcomes. With that probability bell curve, standard deviation is the number of units to the left and right of the average. 68% of outcomes will fall within 1 standard deviation of the average, 95% of outcomes fall within 2 standard deviations and 99.7% fall within 3 standard deviations.

By crunching the numbers and taking into account all of the rules of blackjack, mathematicians a lot smarter than me have concluded that with basic strategy, blackjack has a standard deviation of approximately 1.14.

So what does that mean? Remember that the bell curve shows odds on both sides (win, lose) of the house edge. If you look at the 0.5% house edge, that means that in a single hand of blackjack you will win or lose lose 1.14 betting units or less 68% of the time, win or lose 2.28 betting units (2 standard deviations) 95% of the time and 3.42 betting units 99.7% of the time.

The possible outcomes and variation from the house edge is also affected by the number of hands you play, with the more hands you play bringing you closer to the average. By including the variable of how many hands you play, you can predict the likelihood of winning or losing certain amounts of units over that number of hands. To calculate that, use the following formula:

Take the square root of the total hands played and multiply by 1.14.

Now let’s say you play 200 hands of blackjack. Using that formula, you get a standard deviation of 16.12. Now let’s say you bet $1 on each hand for 200 hands. Since there is a 0.5% house edge, you can expect to lose $1 (1 unit) during that time. But you won’t always have a $1 net loss when betting $1 each hand for 200 hands. What about other outcomes? Playing 200 hands, you can expect to win or lose up to 16.12 units 68% of the time, win or lose up to 32.24 units 95% of the time and win or lose up to 64.48 units 99.7% of the time.

How often will you lose $30, for example?

First, you have to calculate the difference between the expected loss (1) and the actual loss (30). In this case, the difference is 29. You then take the difference and divide by 16.12 (the standard deviation):

29 / 16.12 =   1.799

In this example, 1.799 is a little less than two standard deviations. Taking that into account, you could win or lose $30 or less 95% of the time. Therefore, if you have a day where you win or lose $30, it’s not really uncommon.

What about losing $45, though? 45 / 16.12 = 2.79. That means it falls outside of two standard deviations and is almost 3 standard deviations. Outcomes fall within 2 standard deviations 95% of the time, which means they only fall outside of 2 standard deviations 5% of the time. Therefore, if you lose $45 when playing 200 hands using basic strategy, it just wasn’t your day, because an outcome like that only happens 5% of the time.

Blackjack Strategy: Read the Rules

Thursday, April 22nd, 2010

Most people know that you can’t sit down at a blackjack table without knowing what you’re doing and make money. Just randomly picking what to do in blackjack results in a house edge of, oh, I don’t know, probably around 90%.

Okay, admittedly, I made up that number. I don’t know what the house edge would be in that situation, but it would be very high. Most people know that you have to memorize blackjack basic strategy and stick to it, but even then the casino has a slight advantage (0.5%), unless you count cards correctly.

There is one part of blackjack strategy that people often forget, though, and that is to read the rules. Let me make this very clear. Not all blackjack tables have the same rules. There are countless variations in the rules in both online casinos and the brick and mortar variety. Therefore, you should not assume that you know what the rules are for that particular blackjack game. Unless you have played at that particular table enough times that you know the rules already, you should always familiarize yourself with the rules before you play.

Rules variations can significantly affect the house edge and your decisions. Though a natural blackjack traditionally pays 3:2, some table pay 6:5 and I’ve even seen even money tables. At some tables the dealer will hit a soft 17 while at others he will stand. Some tables will allow you to split any pair, while others will only allow you to split tens or nines and tens. Some blackjack games let you resplit while others don’t. Some blackjack games offer insurance and late surrender, while others do not. Those are just a few of the many rule variations you will find at blackjack tables.

For that reason, you need to familiarize yourself with the rules before you play. At a brick and mortar casino, you can usually find the rules clearly printed on the table itself. If you’re unsure about any rules, feel free to ask the dealer. For online blackjack, it is even easier, because you can simply go to a section of the website that explains the rules. If you have any questions, you can contact customer service. You should never play blackjack without knowing all of the rules for that game ahead of time.

By knowing the rules, you can make sure you don’t make an error in judgment and make sure you are following the correct strategy. In addition, it helps you know whether that is even a blackjack table at which you want to play. If the rules aren’t good, you might want to find somewhere else to play. But you will never know that if you don’t check.