Building a primeIntermediate
A prime is a run of consecutive points you own. Six in a row is the strongest structure in backgammon, because no die shows more than six, so nothing trapped behind it can move at all. Understanding primes is the step from playing moves to playing a plan.
Why six is the magic number
Dice go to six. A checker sitting behind six consecutive made points has no legal escape with any single die, and since checkers move one die at a time, it cannot get out at all. It stays there until you break the prime, which you eventually must when bearing in, and by then you should have won the race.
Four and five primes are already powerful
You do not need all six. Behind a five-prime, only a six escapes, which is 11 rolls in 36 containing at least one six. Behind a four-prime, fives and sixes escape. Each brick you add roughly halves the escape chances, so a prime is worth building even when you cannot finish it.
Where to build
Primes built in front of the trapped checker are what count. A run of points that your opponent has already passed blocks nothing. This is why the 5-point, bar point and 4-point matter so much: they sit where enemy back checkers still are.
Rolling the prime home
The hard part is not building a prime, it is keeping it while you bring the rest of your checkers around. The technique is to move the prime forward one point at a time, breaking from the rear and remaking at the front, so the trapped checker stays behind it the whole way.
The numbers, computed
Every figure below is enumerated over all 36 ordered outcomes of two dice, not quoted from a table. Shot counts assume the intervening points are open.
| Situation | Rolls that work | Chance |
|---|---|---|
| Hitting a blot 6 pips away | 17 of 36 | 47.2% |
| Hitting a blot 5 pips away | 15 of 36 | 41.7% |
| Hitting a blot 4 pips away | 15 of 36 | 41.7% |
Hitting a blot 6 pips away: Indirect shot: it needs two dice combined.
Hitting a blot 5 pips away: Indirect shot: it needs two dice combined.
Hitting a blot 4 pips away: Indirect shot: it needs two dice combined.
What most players get wrong
Once I have a prime, the game is won.
A prime wins the game only if you can convert it. Many players build a beautiful six-prime, run out of spare checkers to move, and are forced to break it from the front while the trapped checker is still behind. If every one of your other checkers is already home, your next roll dismantles your own wall. Keep spares.
Play a rated game and every decision gets reviewed afterwards against the best move available. The dice are committed before you roll and checkable after, so the number you end up with is a measure of you, not of luck.
Play a rated game freeFrequently asked questions
What is a prime in backgammon?
A run of consecutive points occupied by two or more of your checkers. A six-prime cannot be jumped by any die roll, so an opposing checker behind it cannot move.
How many points do I need for a prime?
Six consecutive points is a full prime. Four and five point primes are already very effective, since they restrict escapes to only the highest numbers.
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