The Race

Backgammon offers many plans, from the blitz to the priming game, but sooner or later a large share of games turn into a pure race. In a race the checkers of both sides have passed each other, there is no more contact, and each player simply wants to bring his men home and bear them off first. No hitting is possible any more, so the only real decisions are about the doubling cube and about how to bring checkers in efficiently.

Before the doubling cube appeared in the 1920s, a race had to be played out to the last checker. The cube changed that: the player who leads can offer a double, and the trailer must decide whether the game is still worth playing at higher stakes. That is why race technique is mostly cube technique.

Elements of a race

A race comes down to two questions:

• When should the leader double (or redouble)?
• When should the trailer take, and when should he pass?

To answer them you need an accurate pip count and a sense of how much your position will waste. This article covers the non-contact race up to the point where all checkers are home; the final stage is covered in the bear-off.

Wastage

Two positions with the same pip count are not always equal. A checker can only be borne off once, and any pips a roll spends beyond what is needed are wasted. The main sources of wastage are:

• Gaps. If one of your home points is empty and you roll that number, you have to move a checker down instead of bearing one off.
• High stacks. Many checkers on a few points create gaps elsewhere and reduce your flexibility.
• Stacks on low points. Checkers piled on the 1- and 2-points have a low pip count but still need a whole roll per two checkers. Eight checkers on the 1- and 2-points take four rolls to bear off, while three checkers spread on the 2-, 4- and 5-points with a similar count may need only two.

When bearing in, aim for a smooth spread across the 6-, 5- and 4-points rather than dumping checkers deep.

The 8-9-12 rule

The simplest widely used race guideline is the 8-9-12 rule, popularized by Walter Trice. Measure the leader's advantage as a percentage of his own pip count:

• With a lead of about 8 percent, the leader has a minimum initial double.
• With about 9 percent, he has a minimum redouble.
• Up to about 12 percent, the trailer can still take. Beyond that, it is a pass.

Example: you are on roll with 100 pips and your opponent has 109. Your lead is 9 pips, or 9 percent. That is a double, and even a redouble if you already own the cube, but your opponent still has a take. The rule works best in longer races, roughly 100 pips and up; in short races the numbers shift and the next method is more reliable.

The Keith count

The Keith count, devised by Tom Keith, adjusts the raw pip count for wastage. For each player, start with the pip count and:

• add 2 pips for each checker more than one on the 1-point;
• add 1 pip for each checker more than one on the 2-point;
• add 1 pip for each checker more than three on the 3-point;
• add 1 pip for each empty 4-, 5- or 6-point.

Then increase the adjusted count of the player on roll by one-seventh. Compare the two numbers:

• The player on roll should double if his count exceeds the opponent's by no more than 4.
• He should redouble if it exceeds the opponent's by no more than 3.
• The opponent should take if the roller's count exceeds his by at least 2. Otherwise he should pass.

Example: after adjustments you have 77 and your opponent has 84, and you are on roll. One-seventh of 77 is 11, so your count becomes 88. It exceeds 84 by 4: an initial double is correct, a redouble is not yet, and since 4 is at least 2, your opponent should take.

The one-seventh increase applies only to the player on roll.

Limits of the rules

These guidelines are designed for money play with a centered or owned cube and no gammons possible. In match play the score can change the right decision a great deal, and positions with big stacks or awkward gaps can fool any formula. Modern bots such as GNU Backgammon and eXtreme Gammon give exact race evaluations, and checking a few of your own races with them is the fastest way to learn when the rules of thumb hold. For the cube itself, see the doubling cube.

Summary

• Count the race and look for wastage: gaps, stacks, checkers piled on low points.
• For a quick estimate use 8-9-12: double at 8 percent, redouble at 9, pass beyond 12.
• For a more precise answer use the Keith count: adjust, add one-seventh for the roller, then double within 4, redouble within 3, take if the gap is 2 or more.