Backgammon is a game that requires little introduction. The rules to it similarly require less explanation than more materially complicated games such as chess and permit less variance. Nonetheless there exist some adaptations and customisations of the basic format, which we shall introduce. The simplicity stems from the simplicity of the playing equipment.

The backgammon board itself is well recognisable, distinguished by twenty-four triangles, referred to as points, divided into two courts of twelve. Each player retains fifteen counters, traditionally coloured black and white. The right hand court is itself divided into the home board of black, on the upper half, and white's home board, on the lower. The left hand court is divided in the same way into the two players' outer boards.

Backgammon setup

The points are ordered from white's perspective: the rightmost point in white's inner court is the first, with the rest ordered clockwise therefrom. The checkers are distributed with five on the sixth point, three on the eighth, five on the thirteenth, and two on the twenty-fourth. Black's checkers are distributed symmetrically. Two dice are used throughout the game, with each player rolling one initially until two distinct integers are rolled. The player with the higher roll starts with the two numbers rolled.

Gameplay

The two numbers rolled each time may be treated as separate rolls, with any counter advanced number of points given by one die: clockwise for white, anticlockwise for black. A second counter may be advanced the number given by the second die, or the number may be simply added to the progression of the initial counter. Further, a double roll is used twice, with the number on the dice signifying four rolls to be used at the player's discretion. For example, a roll of two fives would entitle the player to four separate rolls of five, to be used separately or in combinations as desired. Each counter:

• may not move onto any point with multiple oppositely coloured counters;
• may move onto any point with a single oppositely coloured counter, evicting the counter onto the bar;
• may only use as many rolls as can be used legally:
  • for example, if only a three can move a counter, a roll of a three and a five would permit the three to be used, with the five discarded;
  • if no legal move is possible, the player's turn is omitted, with the opponent rolling and moving repeatedly until a player's legal move is possible under a certain roll;
• may not move while any counters are on the bar, in which case rolls may only be used to move counters into the opponent's home board, with a roll of n moving a counter onto the opponent's nth point.

Counters are moved around the board until all fifteen lie within the player's home board.

Removing pieces

The objective is to remove all one's pieces from the gameboard via the home board. A counter:

• may be removed when and only when all non-removed counters are within the player's home board;
• may be removed from the nth point by a roll of:
  • n, or;
  • n or higher, whenever there are no counters on any higher points: for example, when the highest point with any counters is the fourth, a roll of three will remove a piece on the third point, while a roll of four, five, or six will remove a piece from the fourth;
• may be moved within the home board instead of removing a piece, or whenever removing one is impossible.

When all pieces have been removed in this way, the game is won.

Playing for a stake

A stake is often used, in which case a doubling cube is usually employed for recording purposes. The cube displays the first six (non-zero) powers of two, from two to sixty-four. Initially a unit stake is played for, until a player chooses to offer to double the stake, at which point:

• the opponent accepts, and
  • the value of the stake is displayed on the cube if sixty-four or less, or;
  • the value is otherwise recorded;
  • the opponent retains the cube, and if or when the stake is next doubled it at their discretion, or;
  • the opponent declines, forfeiting the game and the current stake.

When the game is won by a player, either:

• the opponent has removed at least one counter from the board, and loses the displayed stake, or;
• the opponent has removed no counters from the board, and either:
  • is gammoned: they have all their counters within the first eighteen points, and loses double the displayed stake;
  • is backgammoned: they have at least one piece within the victor's home board or on the bar, and loses triple the displayed stake.

Popular variations

There exist a variety of variations on the vanilla backgammon rules. One variant is the Dutch version of Backgammon, which generally slows the pace of the game with two rule changes:

• All counters start off the board, and must be moved on in the usual way;
• An opponent's counter singly occupying a point may be removed only when at least one of the player's counters has progressed into their home board.

A yet more innovative popularised in the US military is known as Acey Deucey, where:

• As in the Dutch version, all counters begin off the board;
• No requirement exists to move only counters off the board onto it, whenever there are any;
• The sum forfeited is the stake multiplied by the number of counters still on the board;
• No doubling takes place, expect (according to some rules) whenever an acey deucey – a one and a two – is rolled, at which point:
  • the one and two are played as usual;
  • if both the one and two have been legally played, a double of the player's choosing is played: that is, four of the same number;
  • if all four such rolls have too been played, the dice are rolled again.

Further variations tend to modify the doubling procedure in some way, often to make the game flow more efficiently. This may occur especially at instances of playing backgammon online. For example, the doubling and tripling of the stake for gammons and backgammons respectively may be omitted, a double on the initial roll may trigger an automatic doubling, and a player may have the option, when accepting a doubling, or automatically reciprocating the offer.