Mentor System

Mentor System for Counting Cards in Blackjack

If you've read our page about the KISS Card Counting Systems, you're familiar with the name Fred Renzey, author of Blackjack Bluebook II – The Simplest Winning Strategies Ever Published. He's created several different counting systems, each with a different reason for being. One of these is the Mentor System, which is meant to be useful in both single deck blackjack games and games dealt from multiple decks.

The rest of this page looks at how you would use the Mentor System to count cards in a blackjack game and get an edge over the house. It also compares the Mentor System to some of the other popular card counting systems in use.

How to Count Cards Using the Mentor System

You've probably already read our main card counting page. On it, we explain in detail how counting cards works. We'll provide only the briefest of summaries on this page.

Card counting takes advantage of the fact that a deck of cards has a memory of sorts. Once a card has been dealt, it's no longer in the deck. This changes the odds.

Since blackjack pays 3 to 2, some cards are better for the players than others. When the deck has proportionally more of those cards (the aces and the 10s), then the player has an edge over the casino. Counters raise their bets in order to get more money into action so they can cash in on the likelihood of that higher payout.

Some strategy decisions change based on the proportion of high cards to low cards in the deck, too. For example, basic strategy players never take insurance, but when the count is positive (meaning there are lots of high cards in the deck), taking insurance becomes a positive expectation decision.

Contrary to what some movies might make you think, counting cards doesn't involve memorizing which cards have been played in order to know which cards are still in the deck. Instead, you keep a running count of how many high cards versus low cards have been played.

In the Mentor System, the values of each card are as follows:

  • Aces and 9s are counted as -1
  • 2s and 7s are counted as +1
  • 3s, 4s, 5s, and 6s are counted as +2
  • 10s are counted as +2
  • The only card that counts as a 0 is the 8

You'll notice a couple of things about these values. One is that some cards are worth 2 and some cards are only worth 1 (positive or negative). That makes this a multi-level system, which, by its nature, is harder to use than a single level system. An example of a single level system is the Hi-Lo Count, where each of the cards counts as +1 or -1. There are no other values to memorize.

You're less likely to have noticed that the total values all add up to 0. If you count through an entire deck, or even multiple decks, using these values, you should wind up with a total of 0 when you finish. That makes this a "balanced count".

Since this system is designed to be especially effective when dealing with multiple decks of cards (shoe games), you'll need to be able to convert a running count to a true count.

What does that mean?

The running count is the ongoing tally that you're keeping in your head. But it doesn't take into account that with multiple decks, the effect of removing a single card from the deck is diluted by the greater number of cards in the deck.


If you're playing in a single deck blackjack game, and all 4 aces are dealt out of the deck, then your odds of getting an ace (and/or a blackjack) become 0%.

But if you're playing in a 6 deck game, there are still 20 aces left in the deck. Yeah, your odds of being dealt an ace and/or a blackjack have been reduced, but they haven't been eliminated.

In most card counting systems, you divide the running count by the number of decks remaining in the shoe in order to get a true count. You use the true count to decide how much to raise your bet and how to adjust your strategy decisions.

But in the Mentor Count, you divide the running count by the number of double decks left in the shoe. That takes into account the values assigned to the cards.

Some counters find this easier and more intuitive; others find it hard to remember.

How Effective Is the Mentor Count at Getting an Edge?

The main way most card counting systems get a player an edge over the casino is by letting the player know when she should raise her bets. That's because a deck rich in aces and tens is more likely to result in a blackjack for the player. And since a blackjack pays out at 3 to 2, the player's edge increases.

The accuracy of this estimate is measured using a score called "betting correlation". You can find the betting correlations of multiple card counting systems compared at Norm Wattenberger's QFIT site. It's a score from 0 to 1, higher being better. The Mentor Count has a betting correlation score of 0.97, making it (in this aspect) one of the most accurate systems for determining when to raise your bets.

Counters also use the count to decide when to alter their decisions about basic strategy and whether or not to take insurance. These are scored as "playing efficiency" and "insurance correlation". The Mentor System scores well in both these areas, too.

The biggest drawback to the Mentor System is the relative difficulty of using the system.

Since this is a multi-level system, it's harder to use than most other systems, which are only single level systems. Also, remembering the difference in calculating the true count from the running count might cause problems for a lot of counters, especially if they're used to other systems.

And of course, fans of unbalanced systems like the Red 7 and the KO System probably prefer unbalanced counts which don't require a conversion at all.


The Mentor System is a powerful system created by Fred Renzey, but it's not powerful enough to warrant using it over one of the simpler systems available. We prefer Renzey's KISS systems, in fact. They also don't require a conversion to a true count, which is one aspect of counting cards we've always had a little trouble with. We don't like division, especially not when done in our heads.

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