21+3 Blackjack Side Bets

By Alex Smith, Last updated Feb 2, 2023

21+3 blackjack is one of the most popular blackjack variations in the world. You will find it offered at almost every land-based casino and online casino. It’s very popular at Las Vegas blackjack tables. It is also very common at online casinos, as it’s based heavily on three-card poker. 

On this page, we will look at what 21+3 blackjack is. We will cover details of the side bet, how it works, and what you need to look for if you choose to play it yourself. First, let’s take a look at what the side bet is.

What Is The 21+3 Blackjack Side Bet?

Long gone are the days when you just played your blackjack hand against the dealers. Today, most casinos offer different blackjack variations, some of which allow you to place side bets. A side bet is an additional wager independent of your main blackjack hand. This means that if you draw too many cards and go bust, your side bet wager would still be in play, resulting in you winning.

21+3 blackjack is, by far, the most popular side bet available at the blackjack table. It may seem complex on the surface, but you will realize it’s straightforward once you understand how it works.

To place the side bet, you simply need to choose the amount you want to wager before the hand begins. The general idea of playing 21+3 blackjack is that you will be using your first two cards and the dealer’s first card to form a three-card poker hand.

Below, we will talk more about the rules of playing 21+3 blackjack. We will also be looking at the different hand rankings and how much you can expect to win from playing the side bet.

What are the Rules?

Every casino uses a slightly different variation of blackjack rules, depending on where it’s located and who the game was developed by. When you play 21+3 blackjack, the main game rules will likely be the same as all of the other tables.

This means you will probably be allowed to double down on a nine, 10, 11, you will be able to split any two identical cards, and the dealer will always draw on soft 17.

The main blackjack game payouts will also be unaffected. Blackjack will continue to pay 2/1, and if you win, you will be paid out at even money. If insurance is available, it will also be charged at the regular price of two times your total wager.

How To Play Blackjack 21+3 (From the Initial Bet) 

21+3 blackjack is incredibly simple and straightforward. You simply choose how much you want to wager on the side bet and begin the blackjack as is customary. You then need to wait for your first two cards and the dealer’s first card to be dealt. Once that has happened, the dealer will evaluate these three cards and pay you if you have a winning hand.

Below, we are going to look at the winning hands. Please note that the payouts we mention below are based on a six-deck of cards being used. Different variations of the game use slightly different rules and, subsequently, have slightly different payouts.

Three of a Kind

  • If your first two cards and the dealer’s first card are of the same value, you have made a three-of-a-kind hand. If the three cards are different suits, the typical payout rate is 25:1. Forming a three-of-a-kind hand is relatively rare, even though the payout rate is not that good. 


  • If your three cards are of the same suit, then you have formed what is known as a flush. This is one of the easiest winning hands to form, and it is typically paid out at 5:1. Some casinos, particularly land-based ones, may offer a slightly higher payout. We have seen casinos paying out up to 8:1 for a flush.
  • It is essential to point out that a flush is only formed when the three cards are non-consecutive. If they are consecutive values and the same suit, then you will have formed what is known as a straight flush. We will cover what a straight flush is and its payouts in just a moment.


  • If your three cards are made up of consecutive values (five, six, seven), you have formed a straight. However, these cards cannot be of the same suit; otherwise, that would be a straight flush, which we will cover in just a moment.
  • A straight, like a flush, is one of the most common winning hands while playing 21+3 blackjack—accordingly, most casinos payout at around 10:1 for a straight.

Straight Flush

  • The second-most valuable hand in 21+3 blackjack is the straight flush. This is formed when your three cards are all consecutive values and the same suit. For example, four, five, and six (all hearts) would be a straight flush. Most casinos pay either 40:1 or 45:1 for a straight flush. The probability of you being dealt a straight flush varies depending on how many decks of cards are used.

Suited Three of a Kind

  • The most valuable hand you can form while playing 21+3 blackjack is a suited three-of-a-kind. This is made when your three cards have the same value and the same suit. This is a very rare occurrence, and most players are lucky to land it even once during an entire night’s session.
  • Every casino has slightly different payout rates for a suited three-of-a-kind, but the minimum, usually, is 100:1. We have seen some casinos offering payout worth as much as 250:1, and some casinos in Las Vegas even award part of a progressive jackpot prize for forming a suited three of a kind.

Odds and House Edge (Attractive Odds and Pay Tables?)

In this section of our post, we will look at the odds and house edge of 21+3 blackjack. Remember, the main gameplay is affected by the specific rules the casino chooses to implement. This section will not cover payouts, odds, or house edges for the main blackjack and; only the side bet.

As a general rule of thumb, the house edge of the 21+3 side bet works out to around 3.24%. However, different casinos have slightly different rule variations, significantly impacting the RTP. Compared to other Blackjack side bets, 21+3 is one of the best. For example, compare it to the perfect pairs side bet, which carries a house edge of up to 16%, and you can see why it is far more popular among serious Blackjack players.

Now, let’s look at the odds and probabilities of forming the various hands. In the following examples, we will be assuming it is a six-deck game. 

  • There are 292,896 possible combinations to make a flush, giving you a probability of 0.0584. The actual odds of forming a flush are 5:1, and most casinos payout at 5:1. There are 155,520 combinations to make a straight. The probability of this works out to 0.03102. Again, most casinos pay out the true odds, which is 10:1.
  • There are 25,272 different combinations to make a 3-of-a-kind hand. This equates to a probability of 0.00504. The odds of being dealt a 3-of-a-kind hand are 30:1, yet most casinos tend to pay out at 33:1.
  • There are 10,368 different combinations to make a straight flush, giving you a probability of 0.00206. Here, the casino does not pay out true odds. The true odds are 40:1, but most casinos only pay out 35:1. This is the first indication of the house edge coming into play.
  • Finally, there are 1040 different combinations to make a suited 3-of-a-kind, equating to a probability of 0.00020. Most casinos payout at the true odds here, which is 100:1.

Is 21+3 Blackjack Better Than The Standard Blackjack Game?

This is an entirely subjective question, and nobody can answer it but yourself. Today, hundreds of different Blackjack games are available, and software providers are continuously creating new concepts. The most important thing is that you are enjoying the games you play.

You should never play a specific casino game or video slot just because it’s popular; when you are gambling, it’s essential that you enjoy yourself. However, if you want our opinion from a mathematical point of view, well, of course, regular blackjack is better.

Any Blackjack game with a side bet will offer you poorer odds than the main version of the game. That’s just basic mathematics. When playing standard blackjack, it is possible to reduce the house edge to below 1% if you play according to basic strategy.

That is just not possible when you place wagers on a side bet. However, 21+3 blackjack does have its advantages over other side bet games. The most significant advantage is that it typically offers the lowest house edge of any Blackjack side bet, so if you do want to place side bets, then 21+3 blackjack is a relatively good choice.

If you want to try 21+3 blackjack, you may want to consider playing a demo version of the game. This is easily found at most online casinos today, and it will allow you to try out the game without risking any of your own money. This will let you know how it works and how the payouts are calculated.

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