Backgammon

Players and equipment

Two players, a board of twenty-four narrow triangles called points in four quarters of six, fifteen checkers each in two colours, two dice apiece and a doubling cube marked 2, 4, 8, 16, 32 and 64. The bar is the ridge down the middle of the board, and the two home boards are the two quarters on the same side of it, one nearest each player: on the walkthrough above, the gold corner is yours and the quarter above it is your opponent's. SquareScores keeps the match score: when a game ends, the winner enters what it was worth in their own column, and the sheet shows who is nearest the line.

The deal

There is no deal. Both players set up the same way: two checkers on your 24-point (the far corner, in your opponent's home board), five on your 13-point (the mid-point), three on your 8-point and five on your 6-point. Your checkers travel from the 24-point round to your home board, points 1 to 6; your opponent's travel the opposite way. To start, each player rolls one die; the higher roll moves first, using both numbers as the opening roll. A tie is rolled again.

Play

Roll two dice and move checkers forward towards your home board by the pips shown: one checker for both numbers in turn, or two checkers for one number each. A double is played four times. You must use both numbers if you can, and if only one can be played it must be the higher. A point held by two or more of your opponent's checkers is blocked to you, and six blocked points in a row are a prime that nothing can pass. A single checker on a point is a blot, and landing on it sends it to the bar; a checker on the bar must re-enter in your opponent's home board — a roll of 3 enters on their 3-point — before anything else may move, and if every entry point you roll is blocked the whole turn is lost.

Once all fifteen of your checkers are in your home board you may bear off. A number removes a checker from that point; a number higher than your furthest checker removes that one; a number with no checker on its point and checkers still above it must be played as an ordinary move inside the board. If a checker is hit while you are bearing off, it must come round again before you may go on. The first to bear off all fifteen wins the game.

The doubling cube

Doubling

Game worth twice as much

Before you roll, offer to double the stake; the cube passes to your opponent

Taking

Play on

Accept the double and own the cube; only the owner may redouble

Dropping

Game lost

Refuse the double and concede at the stake before it

Scoring

The winner scores each game in their own column; the loser enters nothing. Multiply the game by the cube.

Single game

1

The loser has borne off at least one checker

Gammon

2

The loser has borne off nothing

Backgammon

3

The loser has borne off nothing and still has a checker on the bar or in the winner's home board

Cube

2, 4, 8

Each double in play doubles the game's value

A worked match

A match to seven. Alice wins the first game as a single game with the cube untouched, and enters 1. In the second game Ben doubles early, Alice takes, and Ben goes on to win a gammon: 2 for the gammon times 2 for the cube, so Ben enters 4. Alice wins the third game with the cube at 2, another single, and enters 2: the score is Alice 3, Ben 4. Alice doubles in the fourth game and Ben drops, which is worth the stake before the double, so Alice enters 1 and leads 4–4 on points but with the momentum. Ben wins the fifth game as a single with the cube at 2 and enters 2: Ben 6, Alice 4. Ben is now one short of seven, so the cube stays in its box for the sixth game — the Crawford rule. Ben wins it, enters 1, and takes the match 7–4.

Ending

A match is played to a set number of points, seven by default; the host sets the line when the game is launched and can move it during the evening. First past the line takes the match, and the next match starts from nothing. In match play, once a player is one point short of the line the cube is put away for the following game only, which is the Crawford rule.

The first roll

The best thing a first roll can do is make a new point in front of your home board, because two checkers together cannot be hit and block your opponent's way past. Look for a roll that lets two of your checkers land on the same empty point: with a 3 and a 1, move one checker three from your 8-point and one checker one from your 6-point, and both land on your 5-point, the most useful point on the board. A 4 and a 2 does the same onto your 4-point; a 6 and a 1 makes the point just outside your home board. If your roll makes no point, do two smaller jobs instead: move one checker off the big stack on your 13-point so it is ready to make a point next turn, and move one of your two back checkers a step forward so they are not stuck together at the far end.

Build a wall

The game is a race, but the first half of it is about blocking. Every point you hold in front of your opponent's two back checkers is one more number they cannot use to get past, and points side by side are a wall: six in a row and they cannot get out at all until you break it. Make new points with checkers that are already out on their own rather than by splitting up a point you hold, and keep a spare checker or two within six spaces of the point you want next, so an ordinary roll can make it.

Lone checkers

A checker on its own can be hit and sent back to the start. That is a risk worth taking early, when your opponent's home board is still mostly empty and a checker sent back can come in again easily, and a risk to avoid late, when their home board is full and a checker on the bar may not get back in for several turns. The further a lone checker is from the enemy, the safer it is: one six away can be hit by almost half of all rolls, one space away by fewer than a third. Hitting your opponent is good when it costs them a whole turn or lets you make a point in the same move; it is bad when it leaves two of your own checkers alone to be hit back.

When to double, and when to take

The cube decides more matches than the dice. Offer a double when you are clearly winning but not yet certain to win, something like three chances in four: offer it earlier and your opponent accepts a cheap gamble, offer it later and they simply give up a game you would have won for double. Accept a double whenever you still have about one chance in four, because giving up costs you one point for certain, while playing on risks two points for a real chance of winning two. In a plain race, add up how many spaces each side still has to move; if you are ahead by about a tenth, double, and if you are behind by less than about an eighth, accept.

Bearing off

Spread your checkers across your home board rather than piling them on the highest point, so that every number you roll takes a checker off. Given a choice, take a checker off the board instead of moving one down inside it. If your opponent still has a checker in your home board, never leave one of yours on its own where it can be hit, even if that wastes a roll: a checker hit this late has to go all the way round again, and that usually loses the game.

Money play

Without a match line, each game is played for its own stake and the cube has no Crawford restriction. Two extra rules are common: the Jacoby rule, under which a gammon or backgammon counts only if the cube has been turned, so nobody plays on for a gammon at 1 point; and beavers, where a player who takes a double may immediately redouble and keep the cube.

Automatic doubles

If the opening roll is a tie, the cube starts at 2 rather than the tie being rolled again. Usually limited to one automatic double a game, and only in money play.

Acey-deucey

The American forces' game. Nothing starts on the board — checkers enter from the bar — and a roll of 1-2 is played as 1-2, then any double of the player's choice, then another roll. A more open, more violent game.

Nackgammon

Set up with two checkers on the 23-point and two on the 24-point, four on the 13-point, three on the 8-point and four on the 6-point. Four back checkers instead of two make the opening slower and the middle game longer, which is the point.

Hypergammon

Three checkers each, starting on the 24-, 23- and 22-points. Games take a few minutes and the cube turns constantly; the whole game has been solved by computer.

Tavla and other tables games

Turkish tavla is backgammon with no doubling cube, no backgammon score and a rule that you may not hit in your opponent's home board on some tables. Greek tavli is three games played in rotation. Under any of them SquareScores keeps the same running score; set the target to suit the house.

How do you set up a backgammon board?

Each player has two checkers on their 24-point, five on the 13-point, three on the 8-point and five on the 6-point. Your 24-point is the far corner of your opponent's home board and your 6-point is in your own home board, so the two sides mirror each other across the bar.

Who goes first in backgammon?

Each player rolls one die. The higher roll moves first and plays those two numbers as the first move. A tie is rolled again, and in money play some tables turn the cube to 2 on a tie instead.

What is a gammon and a backgammon?

A gammon is a win where the loser has not borne off a single checker, worth double. A backgammon is a gammon where the loser still has a checker on the bar or in the winner's home board, worth triple. Both are multiplied by the cube.

How does the doubling cube work?

Before your roll, you may turn the cube to double the value of the game. Your opponent either takes, plays on at the doubled value and owns the cube, so only they may double next; or drops, and loses the game at the value before the double. The cube starts in the middle at 64, which means 1.

What is the Crawford rule?

In a match, when one player is exactly one point short of winning, the next game is played without the cube. After that game the cube comes back. It stops the player behind from doubling at once with nothing to lose.

Can you move a checker onto a point with one opposing checker?

Yes. A single checker is a blot, and landing on it hits it: it goes to the bar and must re-enter in your home board before its owner may move anything else. A point with two or more opposing checkers is blocked.

Do you have to use both dice?

Yes, if you legally can. If either number can be played but not both, you must play the higher. A double is played four times, as far as it can be.

How many points is a backgammon match?

Whatever is agreed: seven is a common evening's match, five for a quick one, and tournaments play to eleven or more. The host sets the line in SquareScores when the game is launched.