Backgammon is a game for two players, played on a board consisting of twenty-four narrow triangles called points. The triangles alternate in color and are grouped into four quadrants of six triangles each. The quadrants are referred to as a player's home board and outer board, and the opponent's home board and outer board. The home and outer boards are separated from each other by a ridge down the center of the board called the bar.

The points are numbered for either player starting in that player's home board. The outermost point is the twenty-four point, which is also the opponent's one point. Each player has fifteen pieces of his own color. The initial arrangement of pieces is: two on each player's twenty-four point, five on each player's thirteen point, three on each player's eight point, and five on each player's six point.

Both players have their own pair of dice and a dice cup used for shaking. A doubling cube, with the numerals 2, 4, 8, 16, 32, and 64 on its faces, is used to keep track of the current stake of the game.

To start the game, each player throws a single die. This determines both the player to go first and the numbers to be played. If equal numbers come up, then both players roll again until they roll different numbers. The player throwing the higher number now moves his pieces according to the numbers showing on both dice. After the first roll, the players throw two dice and alternate turns.

The roll of the dice indicates how many points, or pips, the player is to move his pieces. The pieces are always moved forward, to a lower-numbered point. The following rules apply:

1. A piece may be moved only to an open point, one that is not occupied by two or more opposing pieces.
2. The numbers on the two dice constitute separate moves. For example, if a player rolls 5 and 3, he may move one piece five spaces to an open point and another piece three spaces to an open point, or he may move the one piece a total of eight spaces to an open point, but only if the intermediate point (either three or five spaces from the starting point) is also open.
3. A player who rolls doubles plays the numbers shown on the dice twice. A roll of 6 and 6 means that the player has four sixes to use, and he may move any combination of pieces he feels appropriate to complete this requirement.
4. A player must use both numbers of a roll if this is legally possible (or all four numbers of a double). When only one number can be played, the player must play that number. Or if either number can be played but not both, the player must play the larger one. When neither number can be used, the player loses his turn. In the case of doubles, when all four numbers cannot be played, the player must play as many numbers as he can.

A point occupied by a single piece of either color is called a blot. If an opposing piece  lands on a blot, the blot is hit and placed on the bar.

Any time a player has one or more pieces on the bar, his first obligation is to enter those piece (s) into the opposing home board. A piece is entered by moving it to an open point corresponding to one of the numbers on the rolled dice.

For example, if a player rolls 4 and 6, he may enter a piece onto either the opponent's four point or six point, so long as the prospective point is not occupied by two or more of the opponent's pieces.

If neither of the points is open, the player loses his turn. If a player is able to enter some but not all of his pieces, he must enter as many as he can and then forfeit the remainder of his turn.

After the last of a player's pieces has been entered, any unused numbers on the dice must be played, by moving either the piece that was entered or a different piece.

Once a player has moved all of his fifteen pieces into his home board, he may commence bearing off. A player bears off a piece by rolling a number that corresponds to the point on which the piece resides, and then removing that piece from the board. Thus, rolling a 6 permits the player to remove a piece from the six point.

If there is no piece on the point indicated by the roll, the player must make a legal move using a piece on a higher-numbered point. If there are no pieces on higher-numbered points, the player is permitted (and required) to remove a piece from the highest point on which one of his pieces resides. A player is under no obligation to bear off if he can make an otherwise legal move.

A player must have all of his active pieces in his home board in order to bear off. If a piece is hit during the bear-off process, the player must bring that piece back to his home board before continuing to bear off. The first player to bear off all fifteen pieces wins the game.

Backgammon is played for an agreed stake per point. Each game starts at one point. During the course of the game, a player who feels he has a sufficient advantage may propose doubling the stakes. He may do this only at the start of his own turn and before he has rolled the dice.

A player who is offered a double may refuse, in which case he concedes the game and pays one point. Otherwise, he must accept the double and play on for the new higher stakes. A player who accepts a double becomes the owner of the cube and only he may make the next double.

Subsequent doubles in the same game are called redoubles. If a player refuses a redouble, he must pay the number of points that were at stake prior to the redouble. Otherwise, he becomes the new owner of the cube and the game continues at twice the previous stakes. There is no limit to the number of redoubles in a game.

At the end of the game, if the losing player has borne off at least one piece, he loses only the value showing on the doubling cube (one point, if there have been no doubles). However, if the loser has not borne off any of his pieces, he is gammoned and loses twice the value of the doubling cube. Or, worse, if the loser has not borne off any of his pieces and still has a piece on the bar or in the winner's home board, he is backgammoned and loses three times the value of the doubling cube.

1. Automatic doubles. If identical numbers are thrown on the first roll, the stakes are doubled. The doubling cube is turned to 2 and remains in the middle. Players usually agree to limit the number of automatic doubles to one per game.
2. Beavers. When a player is doubled, he may immediately redouble (beaver) while retaining possession of the cube. The original doubler has the option of accepting or refusing as with a normal double.
3. The Jacoby Rule. Gammons and backgammons count only as a single game if neither player has offered a double during the course of the game. This rule speeds up play by eliminating situations where a player avoids doubling so he can play on for a gammon.

1. A turn is completed when the player picks up his dice. If the play is incomplete or otherwise illegal, the opponent has the option of accepting the play as made or of requiring the player to make a legal play. A play is deemed to have been accepted as made when the opponent rolls his dice or offers a double to start his own turn.
2. If a player rolls before his opponent has completed his turn by picking up the dice, the player's roll is voided. This rule is generally waived any time a play is forced or when there is no further contact between the opposing forces.