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# Blackjack Deck Estimation – Dividing Decks and the True Count

Staff Writer 11/08/2021 Blog 24 views

If you’re using a card counting blackjack strategy, keeping up with the running count is essential. It’s a simple enough concept – you just need to be aware of how advantageous the remaining shoe is based on the cards that were played through. In fact, we already covered the topic in the past. However, there is yet more to learn about this essential part of winning blackjack strategies – blackjack deck estimation.

Let’s take a closer look at how to keep a running count in blackjack and use it to your advantage. More precisely, we’ll learn how to keep an eye on the so-called True Count.

## Blackjack Deck Estimation and the True Count

Keeping a running count is a matter of focus, and it gets easy after some practice. However, applying the knowledge you gain by counting is a wholly different matter.

First of all, a short reminder – a running count is different from the so-called “true count.”  The latter is arguably more useful because it accounts for the different characteristics of multi-deck shoes. Thankfully, it’s also rather easy to explain.

The true count in blackjack is simply your running count divided by the number of decks still in play. Figuring out how many decks are in play is called blackjack deck estimation.

For example, let’s say you’re playing an 8-deck shoe and you’re more than 54 cards into the shoe. Your running count is a solid +14, which sounds amazing on paper. However, there are still 7 decks to deal with. That would make your blackjack card count +2, which is a rather small advantage. Assuming you’re playing a strategy like Hi-Lo, of course.

However, this brings up another point. Just how many decks are currently in play? For instance, imagine 75 cards have passed through. That’s clearly more than 1 deck, but not quite 2. Rounding the number both up and down can completely change your future strategy.

For example, rounding up may cause you to pay too conservatively and lose out on the card counting advantage. Conversely, rounding down may cause you to believe you have a bigger advantage than you actually do.

That’s why most blackjack card counting experts divide decks into halves, quarters, or even eights. It’s a simple matter of, say, counting every 27 cards as a 0.5 deck. There are multiple approaches to blackjack deck estimation, and we’ll cover them below.

## Dividing Decks for Blackjack Card Counting

There are three common ways in which blackjack card counters divide the decks in any given shoe.

• Full-deck division – increasing the true count divisor once for every 54 cards.
• Half-deck division – increasing the true count divisor once for every 27 cards.
• Quarter-deck division – increasing the true count divisor once for every 14 cards.

Technically, more accurate estimations are possible. However, dividing your running count with 0.25 numbers can be quite challenging. Going even smaller than that would require serious mental gymnastics to actually implement in the true count.

In practice, the more accurate the division – the better. Most simulations estimate that the player advantage generated by a Hi-lo strategy is 1% at the most. This assumes perfect blackjack strategy and a full-deck running count.

Comparatively, a half-deck running count offers 6% better returns than the full-deck count on average. This translates to a 1.06% total player advantage in the same circumstances.  Is the extra effort to keep track of cards worth it? Probably. Remember, blackjack advantage play is about gaining a small edge in the long run.

So, what about quarter-deck division? On average, it offers 7% better returns than a full-deck division. I.e. a 1.07% total player advantage, assuming your hi-lo strategy offers a 1% player edge.

That’s why we don’t really believe a counting quarter-deck is worth it. The extra advantage is negligible by most standards. More importantly, though, dividing by quarters is considerably more difficult than whole and half-numbers. If you don’t believe us, try it yourself. Most of us can easily divide by 0.5 at any moment. Dividing by, say, 0.75 is much more difficult.

In conclusion, increasing the divisor in the true blackjack count formula by 0.5 for every 32 cards is likely the optimal solution. Even if you’re a math prodigy and have no issues doing more accurate estimations, the extra effort is probably not worth it.

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