BASIC GAME RULES

Backgammon is a simple game with deep strategic elements. It does not take long to learn to play, although obscure situations do arise which require careful interpretation of the rules. The playing time for each individual game is short, so it is often played in matches, for example the first to five points. Game and match are used in Backgammon to refer to these distinct elements, as in, "I won two games in a row, but then she won three in a row and I lost the match, three points to two."

In short, players are trying to get all of their pieces past their opponent's pieces. This is difficult because the pieces are scattered at first, and may be blocked or captured by the opponent's pieces.

Each side of the board has a track of twelve adjacent spaces, called points and usually represented by long triangles of alternating (but meaningless) color. The tracks are imagined to be connected across the break in the middle and on just one edge of the board, making a continuous line (but not a circle) of twenty-four points. The points are numbered from 1 to 24, with checkers always moving from higher-numbered points to lower-numbered points. The two players move their checkers in opposite directions, so the 1-point for one player is the 24-point for the other. Some recorded games, however, keep the numbering of the points constant from the perspective of one player.

Each player begins with two checkers on his 24-point, three checkers on his 8-point, and five checkers each on his 13-point and his 6-point.

Note that the board as shown can be flipped horizontally, with starting positions and direction of play likewise flipped but with no changes to the mechanics of gameplay. The two orientations are equally common and game boards are all designed to be played both ways.

Points one to six, where the player wants to get his pieces to, are called the home board or inner board. A player may not bear off any checkers unless all of his checkers are in his home board. Points seven to twelve are called the outer board, points thirteen to eighteen are the opponent's outer board, and points nineteen to twenty-four are the opponent's home board. The 7-point is often referred to as the bar point and the 13-point as the mid point.

At the start of the game, each player rolls one die. Whoever rolls higher starts his first turn using the numbers on the already-rolled dice. In case of a tie, the players roll again. The players alternate turns and roll two dice at the beginning of each turn after the first.

After rolling the dice a player must, if possible, move checkers the number of points showing on each die. For example, if he rolls a 6 and a 3, he must move one checker six points forward and another one three points forward. The dice may be played in either order. The same checker may be moved twice as long as the two moves are distinct: six and then three, or three and then six, but not nine all at once.

If a player has no legal moves after rolling the dice, because all of the points to which he might move are occupied by two or more enemy checkers, he forfeits his turn. However, a player must play both dice if it is possible. If he has a legal move for one die only, he must make that move and then forfeit the use of the other die. (If he has a legal move for either die, but not both, he must play the higher number.)

If a player rolls two of the same number (doubles) he must play each die twice. For example, upon rolling a 5 and a 5, he must play four checkers forward five spaces each. As before, a checker may be moved multiple times as long as the moves are distinct.

A checker may land on any point occupied by no checkers or by friendly checkers. Also it may land on a point occupied by exactly one enemy checker (a lone piece is called a blot). In the latter case the blot has been hit, and is temporarily placed in the middle of the board on the bar, i.e., the divider between the home boards and the outfields. A checker may never land on a point occupied by two or more enemy checkers. Thus no point is ever occupied by checkers from both players at the same time.

Checkers on the bar re-enter the game through the opponent's home field. A roll of 1 allows the checker to enter on the 24-point, a roll of 2 on the 23-point, etc. A player with one or more checkers on the bar may not move any other checkers until all of the checkers on the bar have re-entered the opponent's home field.

When all of a player's checkers are in his home board, he may remove them from the board, or bear them off. A roll of 1 may be used to bear off a checker from the 1-point, a 2 from the 2-point, etc. A number may not be used to bear off checkers from a lower point unless there are no checkers on any higher points. For example, a 4 may be used to bear off a checker from the 3-point only if there are no checkers on the 4-, 5-, and 6-points.

A checker borne off from a lower point than indicated on the die still counts as the full die. For instance, suppose a player has only one checker on his 2-point and two checkers on his 1-point. Then on rolling 1-2, he may move the checker from the 2-point to the 1-point (using the 1 rolled), and then bear off from the 1-point (using the 2 rolled). He is not required to maximize the use of his rolled 2 by bearing off from the 2-point.

If one player has not borne off any checkers by the time his opponent has borne off all fifteen, he has lost a gammon, which counts for twice a normal loss. If a player has not borne off any checkers, and still has checkers on the bar and/or in his opponent's home board by the time his opponent has borne off all fifteen, he has lost a backgammon, which counts for triple a normal loss. Sometimes a distinction is made between pieces in the opponent's home board (triple loss) and pieces on the bar (quadruple loss).

VARIOUS GAME RULES

The doubling cube
To speed up match play and to increase the intensity of play and the need for strategy, a doubling cube is usually used. A doubling cube is a 6 sided die that instead of the numbers 1, 2, 3, 4, 5, 6 on it, has the numbers 2, 4, 8, 16, 32, 64 on it. If a player believes his position to be superior he may, before rolling the dice on his turn, double, i.e., demand that the game be played for twice the current stakes. The doubling cube is placed with the 2 side face up to show that the game's value has been doubled. His opponent must either accept the challenge or resign the game on the spot. Thereafter the right to redouble (double again) belongs exclusively to the player who last accepted a double. If this occurs, the cube is placed with the face of the next power of 2 showing.

The game rarely is redoubled beyond 4 times the original stake, but there is no theoretical limit on the number of doubles. Even though 64 is the highest number on the doubling cube, the stakes may rise to 128, 256, 512 and so on.

Beavers
A common rule allows beavers - the right for a player to immediately redouble when offered the doubling cube, while retaining the cube instead of giving it back up. (The redouble must be called before the originally doubling player rolls the dice.) In this way, the stakes of the game can rise dramatically.

Beavers are commonly allowed when backgammon is played for money game by game, and usually not allowed in matches.

Jacoby Rule
The Jacoby Rule makes gammons and backgammons count for their respective double and triple points only if there has been at least one use of the doubling cube in the game. This encourages a player with a large lead in a game to double, and thus likely end the game, rather than see the game out to its conclusion in hopes of a gammon or backgammon. The Jacoby Rule is widely used in money play, but is not used in match play.

Crawford Rule
The Crawford Rule makes match play much more fair for the player in the lead. If a player is one point away from winning a match, his opponent has no reason not to double; after all, a win in the game by the player in the lead would cause him to win the match regardless of the doubled stakes, while a win by the opponent would benefit twice as much if the stakes are double. Thus there is no advantage towards winning the match to being one point shy of winning, if one's opponent is two points shy!

To remedy this situation, the Crawford Rule requires that when a player becomes one single point short of winning the match, neither player may use the doubling cube for a single game, called the Crawford Game. As soon as the Crawford Game is over, any further games use the doubling cube normally.

Not quite as universal as the Jacoby Rule, the Crawford Rule is widely used and generally assumed to be in effect for match play.

Automatic Doubles
When Automatic Doubles are used, any re-rolls that players must make at the very start of a game (when each player rolls one die) have the side-effect of causing a double. Thus, a 3-3 roll, followed by a re-roll of 5-5, followed by a re-roll of 1-4 that begins the game in earnest, will cause the game to be played from the start with 4-times normal stakes. The doubling cube stays in the middle, with both players having access to it. The Jacoby Rule is still in effect.

Automatic Doubles are common in money games (upon agreement). They are never used in match play.

TOURNAMENT RULES

When backgammon tournaments are held to determine an overall winner, the usual style of competition is match play. Competitors are paired off, and each pair plays a series of games to decide which player progresses to the next round of the tournament. This series of games is called a match.

Matches are played to a specified number of points. The first player to accumulate the required points wins the match. Points are awarded in the usual manner: one for a single game, two for a gammon, and three for a backgammon. The doubling cube is used, so the winner receives the value of the game multiplied by the final value of the doubling cube.

Matches are normally played using the Crawford rule. The Crawford rule states that if one player reaches a score one point short of the match, neither player may offer a double in the immediately following game. This one game without doubling is called the Crawford game. Once the Crawford game has been played, if the match has not yet been decided, the doubling cube is active again.

In this example, White and Black are playing a 5-point match. After three games White has 4 points, which is just one point short of what he needs. That triggers the Crawford rule which says there can be no doubling in next game, Game 4.

There is no bonus for winning more than the required number of points in match play. The sole goal is to win the match, and the size of the victory doesn't matter.

Automatic doubles, beavers, and the Jacoby rule are not used in match play.