Match Play
Backgammon Doubling Cube Study
by Phil Simborg, 2008
Phil Simborg
Like most tournament players I know, I generally apply money game thinking in initial cube decisions when the score is 5-away/5-away or greater. Generally, if it is a double or a take for money, I double or take at that score.

But like most players, I am often making a big mistake with this approach. Match play is not the same as money play for a lot of reasons, but one of the major differences is the price, or affect, of gammons after the cube is turned.

One recent position brought this lesson home to me in a very dramatic way, as my mistaken thinking recently cost me the match in the money-round of a major tournament.

In the position below, the score is 8-8 in a 13 point match. As you know, that would be the same as 0-0 in a 5 point match, or simply put, 5-away/5-away.

I am Black, and White has just doubled me. What would you do?

White doubles.
Should Black take?

As you might have guessed from my introduction, it is correct to pass this double. I took it, because I applied money-game thinking, and while I was correct that this is a take for money, it is a solid drop at this match score.

As you can see below in the Snowie match play evaluation, it is a .062 error to take this cube. What is interesting is that if you look at the money play evaluation beside that, it is a take, and it would be a .045 error to drop the cube.

Match Play Evaluation Money Play Evaluation

In both evaluations, White wins the same number of games and gets the same number of gammons, so what's the difference? To find the answer, we must consider the price of gammons.

It is true that the price of gammons is the same at this match score as for money, but only before the cube is turned. After the cube is turned, in a money game, a gammon is still always worth half a win, or .5, but in a match, the value or cost of a gammon changes greatly depending on the match score and the affect of the odds of winning a match by winning a gammon.

At 5-away/5-away, the cost of gammons is .69 when the cube is on 2. In layman's terms, this means that a gammon is much more costly at this match score than it would be in a money game. If you get gammoned and you are now losing 5-away/1-away Crawford, your odds of winning the match go down to about 15 percent. So a gammon is a very nasty thing to have happen to you at this score.

The evaluation tells us that White will win gammons about 30 percent of the time. If you estimate this properly over the board, and you apply the price of gammons properly, what this means is that the effective cost of the gammons in a money game is 15 (30 × .5) but in a match it is around 21 (30 × .69). That 6 extra points is more than enough to push the decision from a take to a pass. I have played enough money games to have a pretty strong feeling that this is a take, and I simply applied that reasoning in my match.

To me, the moral of this story is that backgammon truly is a more complex game than most people realize, and no matter how long you play or how much you think you know, there is always more to learn. More specifically, the moral of this particular study is that if you really want to be a top tournament player, you must learn, and apply, not only your match equity tables and take points, but also the price of gammons.

Phil Simborg is a fulltime backgammon player and teacher.
You can contact Phil at: or visit his
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