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🎲 Dice used in The Royal Game of Ur


In The Royal Game of Ur, even if you are losing, a few lucky rolls at the right time could win you the game! This page goes through the different types of dice used in the game, and the probabilities of your rolls. Any set of four D2 dice can be used to play The Royal Game of Ur, although tetrahedral dice are the most commonly used. Here, D2 refers to the fact that the dice used have two equally likely outcomes.

Tetrahedral Dice

The most commonly used dice when playing The Royal Game of Ur are the tetrahedral dice, which are dice that are shaped like triangle-based pyramids. Each die has two corners marked with white, and two unmarked corners. After rolling the dice, you can count the number of die with a marked corner facing upwards to get your roll.

Throwing Stick Dice

Example Throwing Stick Dice

Throwing sticks are another type of dice that are commonly used to play The Royal Game of Ur. Throwing stick dice are flat sticks with one side marked. You can then throw the sticks and count the number of sticks with their marked side up. Throwing stick dice are commonly used in another ancient game, Aseb, which is another ancient game that is very similar to The Royal Game of Ur. These two games are so common that they actually both share another name, which is The Game of 20 Squares.

Probability

One die

Die with a marked corner up

When using a single die, there is a 50% chance that it will land with its marked corner or side up. This means that for each individual die, you have a 50/50 chance of getting a one.

Four dice

Die with a marked corner up Die with an unmarked corner up
Die with an unmarked corner up Die with an unmarked corner up

When using four dice, you have to count the results of the four individual die. This means that it is possible to get a total of 0, 1, 2, 3, or 4. The chances of each of these possibilities is respectively 1, 4, 6, 4, and 1 out of 16.

This means that you have a 6.25% chance of rolling a 0, a 25% chance of rolling a 1, a 37.5% chance of rolling a 2, a 25% chance of rolling a 3, and a 6.25% chance of rolling a 4.

0: 6.25%
1: 25%
2: 37.5%
3: 25%
4: 6.25%

If you'd like to understand why these are the probabilities of each roll, the user rodecss on slideshare made a great presentation that goes into detail on calculating the probability of each roll. Check it out here.

Strategy

Now that you know the probability of each roll is not the same, you can likely anticipate that this affects the best strategies to use while playing the game, and it does! Here are some tips for picking the best moves,

1. Avoid two spaces in front of your opponent's pieces

Preferably, we'd avoid putting our own pieces in front of our opponents all the time. Unfortunately though, sometimes you have to make progress and move your pieces in front of your opponents. If you have the option, it is safer to do this by placing your pieces 1 or 3 tiles ahead of your opponent's piece, instead of 2. This will slightly reduce their chances of being able to take your piece on their turn.

It is also valuable to note that if your piece is 4 tiles ahead of your opponent's, it is very unlikely that they will be able to take it! Therefore, instead of moving that piece maybe it would be better to move a new piece onto the board, or develop your less advanced pieces.

2. Place your pieces two spaces behind your opponent's

For the opposite reasons to point 1, if you are looking to take one of your opponent's pieces, it is best to get your pieces two spaces behind theirs. This will give you the best chance of being able to take their piece on your next turn.

More Strategy

If you'd like to learn more about strategy in The Royal Game of Ur, check out RoyalUrAnalysis. It contains detailed analysis of different strategies for playing The Royal Game of Ur through the use of AI.

Play The Royal Game of Ur

Now that you know some probability about the game, give it a go!