Probability Of Winning Blackjack

Probability of getting 17 points from the first two cards is P = 16/221 = 7.23981% in the case of a 1-deck game and P = 96/1339 = 7.16952% in the case of a 2-deck game. A good initial hand (which you can stay with) could be a blackjack or a hand of 20, 19 or 18 points. P both = P blackjack × 3 × 15 ( 50 2). By the inclusion/exclusion principle, the probability of at least one getting blackjack is the sum of probabilities of each individual getting blackjack minus the probability of both getting blackjack (removes redundant overlap): 1 − P either or both = 0.90524.

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Blackjack odds are percentage figures which represent your probability of losing or winning a hand. They can also represent the house edge or their profit margins as well. Usually probability odds don't mean much on the short term, but they clearly average out in the long term and this is why the casinos always win over the long term.

We decided to make a few tables and charts of the most common blackjack probability odds for various scenarios and situations found while playing blackjack. The most important odds percentage represents the dealer's edge in the game. This is the long term advantage that they have which will eventually take your money away. Blackjack is actually one of the most popular games in the casino and also has some of the lowest odds of all the casino games, except casino craps of course. Generally their edge ranges from 1% to 15% depending on what variation of blackjack you are playing.

How to Beat the Casino House Odds

There is one feature that makes blackjack more desirable than any other casino game. There is actually a way to beat the house edge by increasing your odds. In fact, your probability odds in blackjack can be increase to the point where you would actually be making the profit in the long term, essentially turning the casino into a personal ATM. This practice is known as card counting and casinos don't like this because they know they will be losing money.

Before you start card counting, you should learn 'blackjack basic strategy', which is the mathematically correct way to play every move in blackjack to get the best odds. This can lower the house edge to less than 1 percent. When that percentage goes to a negative number such as -1%, then it is you who has the edge over the casino. This is when you complement basic strategy with card counting to get the highest efficiencies.

Odds vs. Dealer Up Card

The first odds chart shows what kind of advantage the player has vs. the dealer based on what his up card is showing. The first column in the chart is what card the dealer has showing after the cards have been dealt. The second column of the table shows the dealer's probability of going bust based on each card. The last column shows the advantage the player has and the probability of winning based on the basic strategy theory. As you can see, the dealer has about a 43% chance of going bust when he has a 5 showing as an up card. At the same time, the player has about 23% advantage as well. Notice that the player advantage goes negative when the 10 cards and ace start showing up. This means the player is more likely to lose.

Dealer's Up Card	Dealer Odds of Busting	Player Advantage Percentage
2	35.30%	9.8%
3	37.56%	13.4%
4	40.28%	18.0%
5	42.89%	23.2%
6	42.08%	23.9%
7	25.99%	14.3%
8	23.86%	5.4%
9	23.34%	-4.3%
10	21.43%	-16.9%
J	21.43%	-16.9%
Q	21.43%	-16.9%
K	21.43%	-16.9%
A	11.65%	-16.0%

Blackjack odds of Busting While Taking a Hit

This chart shows the probabilities of going bust after taking a hit. Busting means that your card total would go over 21 points and would be a hard total as well. The highest score you can get when being initially dealt two cards is 21 points so you can never go bust. This means if you took a hit on a hard 21, you would have a 100% probablity of going bust, which is common sense. Also, if you have 11 points or less, it is impossible to go over 21 points on the next hit and your odds of going bust would be 0 percent.

Total Hand Value	Probability of Going Bust
21	100%
20	92%
19	85%
18	77%
17	69%
16	62%
15	58%
14	56%
13	39%
12	31%
11 or less	0%

House Advantage with Multiple Number of Decks

The number of 52 card decks in a game of blackjack influences the house edge. In some cases, the odds increase in favor of the casino when more decks are used. The advantage edge can be as much as 1% towards the casino and this is a big number in terms of odds over the long term. As you can see here, a single deck of card gives the lowest edge for the casino and gives the player better odds. Multiple decks such as eight decks increases the house edge almost 18 times more than it would for the single deck!

Number of Decks	House Odds Advantage
Single Deck	0.04%
Double Deck	0.42%
Four Decks	0.61%
Six Decks	0.67%
Eight Decks	0.70%

Two Card Frequency Odds

The next odds table deals with the first two cards being dealt or the 2 card frequency odds. Every player is dealt two cards at the beginning of a round of blackjack so this chart tells you the percentage of getting different categories of hands. A natural blackjack is only 4.8%, which essentially is an ace dealt with a ten card straight off the initial deal. Normally the odds are 3 to 2 and you would win $3 for every $2 wagered. It's a small percentage but it's the most desirable hand to get. The lowest hand you can get is two points (two aces). This is part of the decision hands group where players are usually dealt soft hands and can make decisions without going bust. This group is the most common.

The other category is the hard standing hands. These hands are somewhat desirable because of the high scores likely to beat the dealer. These are the second most frequent two card blackjack hands. Finally there is a no bust two card hand. No bust means any two card hand that won't bust on the next hit, such as any soft hand or hard hand that is 11 points or less.

Two Card Combination	Frequency Percentage
Natural 21 Blackjack	4.8%
Hard Standing (17 - 20)	30.0%
Decision Hands (2-16)	38.7%
No Bust	26.5%
Total (all two card hands)	100%

Probability Edge for Each Card Removed from Deck

The next table shows how much your odds improve after when certain cards have been dealt and removed from the deck. Certain cards taken out of the deck and increase or decrease your blackjack odds percentage and the house edge.

This is very important for card counting. If you want the absolute perfect odds in card counting, you have to acount for each small change in the odds whenever a card is dealt. As you can see from the table, when small cards are taken out of play, the odds increase in your favor overall. This is a paramount property of card counting. The opposite happens when large cards are dealt. Your odds begin to decrease. When you are counting cards, you will notice your count decreasing when large cards are dealt.

You can imagine how complicated it would be to be adding these numbers in your head while card counting at the same time. If your mind was a computer, it would be easier to keep track of the percentage. Some people can do this, and this is the way to become a perfect card counter! It is easier to keep track of the odds when playing with a single blackjack deck. For example, when five cards are seen on the table, they offer a 0.67% increase in your advantage. In fact, when a lot of fives are used up, your odds will be much higher than if any of the other low cards were used up, even the six point cards. Also, these effects are cumulative so you always need to keep track of the odds after every card is dealt. This data is actually quite amazing!

Removed Card	Effect on Odds
2	0.40%
3	0.43%
4	0.52%
5	0.67%
6	0.45%
7	0.30%
8	0.01%
9	-0.15%
10	-0.51%
Jack	-0.51%
Queen	-0.51%
King	-0.51%
Ace	-0.59%

Dealer Final Hand Probability Odds

This next table shows the odds of what the dealer's final hand will be. Usually in blackjack, the dealer must hit on 16 and stand on 17. These rules are slightly different for other variations of twenty-one. So generally, the odds of the dealer's final score being 16 are 0% because he must hit. This table will show the probability of the dealer busting or getting a non-bust hand as well as natural blackjacks.

Dealer Final Hand	Probability of Getting Final Hand
Natural Blackjack	4.82%
21 (more than 2 cards)	7.36%
20	17.58%
19	13.48%
18	13.81%
17	14.58%
Non-Bust (less than 21)	71.63%
Bust (more than 21)	28.37%

Click image above to visit CasinoMax and play blackjack (free or real money).

By Ion Saliu, Founder of Blackjack Mathematics

I. Probability, Odds for a Blackjack or Natural 21
II. House Edge on Insurance Bet at Blackjack
III. Calculate Double-Down Hands
IV. Calculate Blackjack Pairs: Strict or Mixed Ten-Cards
V. Free Blackjack Resources, Basic Strategy, Casino Gambling Systems

1.1. Calculate Probability (Odds) for a Blackjack or Natural 21

First capture by the WayBack Machine (web.archive.org) Sectember (Sect Month) 1, 2015.

I have seen lots of search strings in the statistics of my Web site related to the probability to get a blackjack (natural 21). This time (November 15, 2012), the request (repeated 5 times) was personal and targeted directly at yours truly:

'In the game of blackjack determine the probability of dealing yourself a blackjack (ace face-card or ten) from a single deck. Show how you arrived at your answer. If you are not sure post an idea to get us started!'

Oh, yes, I am very sure! As specified in this eBook, the blackjack hands can be viewed as combinations or arrangements (the order of the elements counts; like in horse racing trifectas).

1) Let's take first the combinations. There are 52 cards in one deck of cards. There are 4 Aces and 16 face-cards and 10s. The blackjack (or natural) can occur only in the first 2 cards. We calculate first all combinations of 52 elements taken 2 at a time: C(52, 2) = (52 * 51) / 2 = 1326.

We combine now each of the 4 Aces with each of the 16 ten-valued cards: 4 * 16 = 64.

The probability to get a blackjack (natural): 64 / 1326 = .0483 = 4.83%.

2) Let's do now the calculations for arrangements. (The combinations are also considered boxed arrangements; i.e. the order of the elements does not count).

We calculate total arrangements for 52 cards taken 2 at a time: A(52, 2) = 52 * 51 = 2652.

In arrangements, the order of the cards is essential. Thus, King + Ace is distinct from Ace + King. Thus, total arrangements of 4 Aces and 16 ten-valued cards: 4 * 16 * 2 = 128.

The odds to get a blackjack (natural) as arrangement: 128 / 2652 = .0483 = 4.83%.

4.83% is equivalent to about 1 in 21 blackjack hands. (No wonder the game is called Twenty-one!)

Calculations for the Number of Cards Left in the Deck, Number of Decks

There were questions regarding the number of cards left in the deck, number of decks, number of players, even the position at the table.

1) The previous probability calculations were based on one deck of cards, at the beginning of the deck (no cards burnt). But we can easily calculate the blackjack (natural) odds for partial decks, provided that we know the number of remaining cards (total), Aces and Ten-Value cards.

Let's take the situation heads-up: One player against the dealer. Suppose that 12 cards were played, including 2 Tens; no Aces out. What is the new probability to get a natural blackjack?

Total cards remaining (R) = 52 - 12 = 40

Aces remaining in the deck (A): 4 - 0 = 4

Ten-Valued cards remaining (T): 16 - 2 = 14

Odds of a natural: (4 * 14) / C(40, 2) = 56 / 780 = 7.2%

(C represents the combination formula; e.g. combinations of 40 taken 2 at a time.)

The probability for a blackjack is higher than at the beginning of a full deck of cards. The odds are exactly the same for both Player and Dealer. But - the advantage goes to the Player! If the Player has the BJ and the Dealer doesn't, the Player is paid 150%. If the Dealer has the blackjack and the Player doesn't, the Player loses 100% of his initial bet!

This situation is valid only for one Player against casino. Also, this situation allows for a higher bet before the round starts. For multiple players, the situation becomes uncontrollable. Everybody at the table receives one card in succession, and then the second card. The bet cannot be increased during the dealing of the cards. Hint: try as much as you can to play heads-up against the Dealer!

The generalized formula is:

Probability of a blackjack: (A * T) / C(R, 2)

Odds Of Winning Blackjack With 3 Hits

A = Aces in the deck

T = Tens in the deck

R = Remaining cards in the deck.

2) How about multiple decks of cards? The calculations are not exactly linear because of the combination formula. For example, 2 decks, (104 cards):

~ the 2-deck case:

C(52, 2) = 1326

C(104, 2) = 5356 (4.04 times larger than total combinations for one deck.)

8 (Aces) * 32 (Tens) = 256

Odds of BJ for 2 decks = 256 / 5356 = 4.78% (a little lower than the one-deck case of 4.83%).

~ the 8-deck case, 416 total cards:

C(52, 2) = 1326

C(416, 2) = 86320 (65.1 times larger than total combinations for one deck.)

32 (Aces) * 128 (Tens) = 4096

Odds of BJ for 8 decks = 4096 / 86320 = 4.75% (a little lower than the two-deck situation and even lower than the one-deck case of 4.83%).

There are NO significant differences regarding the number of decks. If we round the figures, the general odds to get a natural blackjack can be expressed as 4.8%.

The advantage to the blackjack player after cards were played: Not nearly as significant as the one-deck situation.

3) The position at the table is inconsequential for the blackjack player. Only heads-up and one deck of cards make a difference as far the improved odds for a natural are concerned.

Axiomatic one, let's cover all the bases, as it were. The original question was, exactly, as this: 'Dealing yourself a blackjack (Ace AND Face-card or Ten) from a single deck'. The calculations above are accurate for this unique situation: ONE player dealing cards to himself/herself. The odds of getting a natural blackjack are, undoubtedly, 1 in 21 hands (a hand consisting of exactly 2 cards).
Such a case is non-existent in real-life gambling, however. There are at least TWO participants in a blackjack game: Dealer and one player. Is the probability for a natural blackjack the same – regardless of number of participants? NOT! The 21 hands (as in probability p = 1 / 21) are equally distributed among multiple game agents (or elements in probability theory). Mathematics — and software — to the rescue! We apply the formula known as exactly M successes in N trials. The best software for the task is known as SuperFormula (also component of the integrated Scientia software package).
Undoubtedly, your chance to get a natural BJ is higher when playing heads-up against the dealer. The degree of certainty DC decreases with an increase in the number of players at the blackjack table. I did a few calculations: Heads-up (2 elements), 4 players and dealer (5 elements), 7 players and dealer (8 elements).
- The degree of certainty DC for 2 elements (one player and dealer), one success in 2 trials (2-card hands) is 9.1%; divided by 2 elements: the chance of a natural is 9.1% / 2 = 4.6% = the closest to the 'Dealing yourself a blackjack (Ace AND Face-card or Ten) from a single deck' situation.
- The chance for 5 elements (4 players and dealer), one success in 5 trials (2-card hands) is 19.6%; distributed among 5 elements, the degree of certainty DC for a blackjack natural is 19.6% / 5 = 3.9%.
- The probability for 8 elements (7 players and dealer), one success in 8 trials (2-card hands) is 27.1%; equally distributed among 8 elements, the degree of certainty DC of a blackjack natural is 27.1% / 8 = 3.4%.
That's mathematics and nobody can manufacture extra BJ natural 21 hands... not even the staunchest and thickest card-counting system vendors! The PI... er, pie is small to begin with; the slices get smaller with more mouths at the table. Ever wondered why the casinos only offer alcohol for free — but no pizza?

1.2. Probability, Odds for a Blackjack Playing through a Deck of Cards

The probabilities in the first chapter were calculated for one trial. That is, the odds to get a blackjack in the first two cards. But what are the probabilities to get a natural 21 dealing an entire deck?

1.2.A. Dealing 2-card hands until the deck is dealt entirely

There are 52 cards in the deck. Total number of trials (2-card hands) is 52 / 2 = 26. SuperFormula probability software does the following calculation:

The probability of at least one success in 26 trials for an event of individual probability p=0.0483 is 72.39%.

1.2.B. Dealing 2-card hands in heads-up play until the deck is dealt entirely

There are 52 cards in the deck. We are now in the simplest real-life situation: heads-up

play. There is one player and the dealer in the game. We suppose an average of 6 cards dealt in one round. Total number of trials in this case is equivalent to the number of rounds played. 52 / 6 makes approximately 9 rounds per deck. SuperFormula does the following calculation:

The probability of at least one success in 9 trials for an event of individual probability p=0.0483 is 35.95%.

You, the player, can expect one blackjack every 3 decks in heads-up play.

2. House Edge on the Insurance Bet at Blackjack

“Insurance, anyone?” you can hear the dealer when her face card is an Ace. Players can choose to insure their hands against a potential dealer's natural. The player is allowed to bet half of his initial bet. Is insurance a good side bet in blackjack? What are the odds? What is the house edge for insurance? As in the case of calculating the odds for a natural blackjack, the situation is fluid. The odds and therefore the house edge are proportionately dependent on the amount of 10-valued cards and total remaining cards in the deck.

We can devise precise mathematical formulas based on the Tens remaining in the deck. We know for sure that the casino pays 2 to 1 for a successful insurance (i.e. the dealer does have Ten as her hole card).

We start with the most easily manageable case: One deck of cards, one player, the very beginning of the game. There is a total of 16 Teens in the deck (10, J, Q, K). The dealer has dealt 2 cards to the player and one card to herself that we can see exactly — the face card being an Ace. Therefore, 52 – 3 = 49 cards remaining in the deck. There are 3 possible situations, axiomatic one:

1) The player has 2 non-ten cards; there are 16 Teens in the deck = the favorable situations to the player if taking insurance. There are 49 – 16 = 33 unfavorable cards to insurance. However, the 16 favorable cards amount to 32, as the insurance pays 2 to 1. The balance is 33 – 32 = +1 unfavorable situation to the player but favorable to the casino (the + sign indicates a casino edge). In this case, there is a house advantage of 1/49 = 2%.
2) The player has 1 Ten and 1 non-ten card; there are 15 Teens remaining in the deck = the favorable situations to the player if taking insurance. There are 49 – 15 = 34 unfavorable cards to insurance. However, the 15 favorable cards amount to 30, as the insurance pays 2 to 1. The balance is 34 – 30 = +4 unfavorable situations to the player but favorable to the casino. In this case, there is a house advantage of 4/49 = 8%.
- This can be also the case of insuring one's blackjack natural: an 8% disadvantage for the player.
- This figure of 8% represents the average house edge regarding the insurance bet. I did calculations for various situations — number of decks and number of players.
3) The player has 2 Ten-count cards; there are 14 Teens in the deck = the favorable situations to the player if taking insurance. There are 49 – 14 = 35 unfavorable cards to insurance. However, the 14 favorable cards amount to 28, as the insurance pays 2 to 1. The balance is 35 – 28 = +7 unfavorable situations to the player but favorable to the casino. In this case, there is a house advantage of 7/49 = 14%. This is the worst-case scenario: The player should never — ever — even think about insurance with that strong hand of 2 Tens!

Believe it or not, the insurance can be a really sweet deal if there are multiple players at the blackjack table! Let's say, 5 players, the very beginning of the game. There is a total of 16 Teens in the deck (10, J, Q, K). The dealer has dealt 10 cards to the players and one card to herself that we can see exactly — the face card being an Ace. Therefore, 52 – (10 + 1) = 41 cards remaining in the deck. There are many more possible situations, some very different from the previous scenario:

1) The players have 10 non-ten cards; there are still 16 Tens in the deck = the favorable situations to the player if taking insurance. There are 41 – 16 = 25 unfavorable cards to insurance. However, the 16 favorable cards amount to 32, as the insurance pays 2 to 1. The balance is 25 – 32 = –7 favorable situation to the player but unfavorable to the casino (the – sign indicates a player advantage now). In this case, there is a house advantage of 7/41 = –17%. The Player has a whopping 17% advantage if taking insurance in a case like this one!
2) The players have 10 Ten-count cards; there are 6 Teens in the deck = the favorable situations to the player if taking insurance. There are 41 – 6 = 35 unfavorable cards to insurance. However, the 6 favorable cards amount to 12, as the insurance pays 2 to 1. The balance is 35 – 12 = +23 unfavorable situations to the player but favorable to the casino. In this case, there is a house advantage of 23/41 = 56%. This is the worst-case scenario: None of the players should ever even think about insurance with those strong hands of 2 Tens per capita!
3) Applying the wise aurea mediocritas adagio, there should be an average of 3 or 4 Teens coming out in 11 cards; thus, 12 or 13 Tens remaining in the deck. There are 41 – 13 = 28 unfavorable cards to insurance. However, the 12.5 favorable cards amount to an average of 25, as the insurance pays 2 to 1. The balance is 30 – 25 = +5 unfavorable situations to the player but favorable to the casino. In this case, there is a house advantage of 5/41 = 12%. Unfortunately, even if we consider averages, taking insurance is a repelling bet for the player.

HA = {(R – T) – T*2} / R

where —

HA = house advantage
R = cards remaining in the deck
T = Tens remaining in the deck.

• Axiomatic one, buying (taking) insurance can be a favorable bet for all blackjack players, indeed. Of course, under special circumstances — if you see certain amounts of ten-valued cards on the table. The favorable situations are calculated by the formula above.
But, then again, a dealer natural 21 occurs about 5%- of the time — the insurance alone won't turn the blackjack game entirely in your favor.

3. Calculate Blackjack Double-Down Hands

Strictly-axiomatic colleague of mine, writing software leads me into new-ideas territory far more often than not. I discovered something new and intriguing while programming software to calculate the blackjack odds totally mathematically. By that I mean generating all possible elements and distinguishing the favorable elements. After all, the formula for probability is the rapport of favorable cases, F, over total possible cases, N

: p = F/N.

Up until yours truly wrote such software, total elements in blackjack (i.e. hands) were obtained via simulation. Problem with simulation is incomplete generation. According to by-now famed Ion Saliu's Probability Paradox, only some 63% of possible elements are generated in a simulation of N random cases.

I tested my software a variable number of card decks and various deck compositions. I noticed that decks with lower proportions of ten-valued cards provided higher percentages of potential double-down hands. It is natural, of course, as Tens are the only cards that cannot contribute to a hand to possibly double down. However, the double-down hands provide the most advantageous situations for blackjack player. Indeed, it sounds like 'heresy' to all followers of the cult or voodoo ritual of card counting!

I rolled up my sleeves and performed comprehensive calculations of blackjack double-downs (2-card hands). The single deck is mostly covered, but the calculations can be extended to any number of decks.

At the beginning of the deck (shoe): Total combinations of 52 cards taken 2 at a time is C(52, 2) = 1326 hands. Possible 2-card combinations that can be double-down hands:

9-value cards AND 2-value cards: 4 9s * 4 2s = 16 two-card possibilities
8-value cards AND 2-value cards: 4 8s * 4 2s = 16 two-card configurations
8-value cards AND 3-value cards: 4 8s * 4 3s = 16 two-card possibilities
7-value cards AND 2-value cards: 4 7s * 4 2s = 16 two-card configurations
7-value cards AND 3-value cards: 4 7s * 4 3s = 16 two-card possibilities
7-value cards AND 4-value cards: 4 7s * 4 4s = 16 two-card configurations
6-value cards AND 3-value cards: 4 6s * 4 3s = 16 two-card configurations
6-value cards AND 4-value cards: 4 6s * 4 4s = 16 two-card combinations
6-value cards AND 5-value cards: 4 6s * 4 5s = 16 two-card possibilities
5-value cards AND 4-value cards: 4 5s * 4 4s = 16 two-card combinations
5-value cards AND 5-value cards: C(4, 2) = 6 two-card hands (5 + 5 can appear 6 ways).
Ace AND 2-value cards: 4 As * 4 2s = 16 two-card combinations
Ace AND 3-value cards: 4 As * 4 3s = 16 two-card possibilities
Ace AND 4-value cards: 4 As * 4 4s = 16 two-card hands
Ace AND 5-value cards: 4 As * 4 5s = 16 two-card possibilities
Ace AND 6-value cards: 4 As * 4 6s = 16 two-card hands
Ace AND 7-value cards: 4 As * 4 7s = 16 two-card combinations.
Total possible 2-card hands in doubling down configuration: 262. Not every configuration can be doubled down (e.g. 4+5 against Dealer's 9 or A+2 against 7).
We look at a double down blackjack basic strategy chart. Some 42% of the hands ought to be doubled-down (strongly recommended): 262 * 0.42 = 110. That figure represents 8% of total possible 2-hand combinations (1362), or a chance equal to once in 12 hands.
The chance for double-down situations increases with an increase in tens out over the one third cutoff count. The probability for a natural blackjack decreases also — one reason the traditional plus-count systems anathema the negative counts. But what's lost in naturals is gained in double downs — and then some.
A sui generisblackjack card-counting strategy was devised by yours truly and it beats the traditionalist plus count systems hands down, as it were.
Be mindful, however, that nothing beats the The Best Casino Gambling Systems: Blackjack, Roulette, Limited Martingale Betting, Progressions. That's the only way to go, the tao of gambling.

4. Calculate Blackjack Pairs: Strict or Mixed Ten-Cards

Probability Of Winning At Blackjack

The odds-calculating software I mentioned above (section III) also counts all possible blackjack pairs. The software, however, considers pairs to be two cards of the same value. In other words, 10, J, Q, K are treated as the same rank (value). My software reports data as this fragment (single deck of cards):

Mixed Pairs: All 10-Valued Cards Taken 2 at a Time

Evidently, there are 13 ranks. Nine ranks (2 to 9 and Ace) consist of 4 cards each (in a single deck). Four ranks (the Tenners) consist of 16 cards. Total of mixed pairs is calculated by the combination formula for every rank. C(4, 2) = 6; 6 * 9 = 54 (for the non-10 cards). The Ten-ranks contribute: C(16, 2) = 120. Total mixed pairs: 54 + 120 = 174. Probability to get a mixed pair: 174 / 1326 = 13%.

Strict Pairs: Only 10+10, J+J, Q+Q, K+K

But for the purpose of splitting pairs, most casinos don't legitimize 10+J, or Q+K, or 10+Q, for example, as pairs. Only 10+10, J+J, Q+Q, K+K

are accepted as pairs

Blackjack Winning Chart

. Allow me to call them strict pairs, as opposed to the above mixed pairs.

There are 13 ranks of 4 cards each. Each rank contributes C(4, 2) = 6 pairs. Total strict pairs: 13 * 6 = 78. Probability to get a mixed pair: 78 / 1326 = 5.9%.Total strict pairs = 78 2-card hands (5.9%, but...).

However, not all blackjack pairs should be split; e.g. 10+10 or 5+5 should not be split, but stood on or doubled down. Only around 3% of strict pairs should be legitimately split. See the optimal split pairsblack jack strategy card.

5. Free Blackjack Resources, Basic Strategy, Casino Gambling Systems