House Rule Explained: Why Both Players Throw Two Dice at the Start

The way we learned to play

In Romania, backgammon is called table, and most of us learned it as children, at a kitchen table or on a summer porch, from parents and grandparents. Nobody opened a rulebook. Both players threw their two dice, the better throw started, and if it was a double, even better: you played it on the spot.

When we built Clean Backgammon, we kept that start. It is a house rule: a local custom that differs from the international tournament rule. It is applied the same way to both players in every mode of the game, and nothing about it is hidden. This article explains exactly how it works and what it means mathematically, so you know what to expect from the very first roll.

How the opening roll works in Clean Backgammon

• Both players throw two dice.

• A double beats a non-double. If you throw 2-2 and your opponent throws 6-5, you start.

• Otherwise the higher total wins. This applies when both throws are doubles or both are not: 5-5 beats 3-3, and 6-4 beats 5-3.

• An equal result is thrown again. For example, 6-2 against 5-3, or 4-4 against 4-4.

• If the winning throw is a double, it is played straight away, four times, like any double.

• If the winning throw is not a double, the winner throws again and plays that new roll, whatever it is.

After that, the game continues normally, and every roll is a single, ordinary throw of two dice.

How this differs from the tournament rule

In the international rule, each player throws one die. The higher die starts, and the starting player plays the two numbers shown (one from each die). Equal dice are thrown again. As a result, a tournament game can never open with a double, and each of the 15 non-double combinations appears in exactly 1 of 15 games.

Both rules are fair: in both, each player has exactly the same chance to start. They simply produce different first moves. If you know the tournament statistics well, our openings will look different, and the next sections show by how much.

The exact numbers

We computed every number below over all 1,296 possible combinations of the four opening dice (6 × 6 × 6 × 6), together with the 36 possible second throws, so they are exact, not simulated.

• Who starts: each player starts exactly 50% of the time. The rule is symmetric, so neither side has an advantage.

• Throw again: 9.4% of opening throws are equal and are thrown again.

• A double played straight from the opening throw: 33.2% of games.

• Starting with a double, in total: 44.3% of games, against 0% under the tournament rule and 16.7% (1 in 6) for a normal roll. That is the 33.2% above, plus the second throw coming up a double 1 time in 6 in the other games.

• Average size of the first move: 10.2 pips, against 7.0 pips under the tournament rule and 8.2 pips for a normal roll.

• Each double starts between 7.0% and 7.8% of games: 6-6 the most often (7.8%) and 1-1 the least (7.0%). Every non-double, from 1-2 to 6-5, starts exactly 3.7% of games: they all come from the second, ordinary throw, so none of them is favoured.

Why the first move has more doubles than a normal roll

If you count only first moves, you will see a double in almost every second game. That is not a sign of biased dice. It is a selection effect: a double always wins the opening against a non-double, and a winning double is kept and played. So a double can reach the first move twice: from the opening throw, and again from the second throw when the opening throw was not a double.

Non-doubles are never kept from the opening throw: they are only played from a fresh, ordinary roll. That is why all 15 non-double combinations are exactly equally likely on the first move, and why big numbers like 6-5 are not favoured. Every individual die is still perfectly fair: each face comes up 1 time in 6, and each of the 36 combinations of two dice comes up 1 time in 36. Only the rule for which throw is played changes.

And this happens only at the start of a game. From the second turn to the last, there is no comparison: each player throws once, and the result is played as it falls.

What it means for your games

• The starting player often gets a strong first move. Opening with 6-6 or 5-5 is a real head start. But each player has exactly the same 50% chance of being that player, so over many games it evens out.

• Opening theory is a little different. Tournament opening tables cover only the 15 non-double rolls. In almost half of our games the first move is a double, so it is worth learning how to play them. Against the AI, use the hint: it is powered by Master, our strongest engine, and shows its best move for any opening.

• Opening statistics are not normal-roll statistics. If you analyse your dice, keep the start of the game separate from the rest, or count all four opening dice. Counting only the throw that won will always show too many doubles.

Check it yourself

You do not have to take our word for it. The My Dice screen in the app (LEADERBOARDS 🏆 → MY DICE) records every roll of your games. For the opening, it records both throws, yours and your opponent’s, not only the one that won, so your statistics are not tilted towards doubles by this rule. Over a large number of rolls, you will see each of the 36 combinations close to 1 in 36 and doubles close to 1 in 6.

The global statistics of online matches are public on our 👉 Dice Fairness page, with the full 6×6 distribution and a Chi-Square test, and our 👉 fair RNG article explains how the dice themselves are generated.

Why we keep it

We like this start. It keeps alive the way backgammon is played at home in many families, and it makes the first move more lively: almost one game in two starts with a double. Most importantly, it is the same rule for everyone, applied the same way by the app, the AI and the server.

Ready to throw your first two dice? 👉 Get Clean Backgammon on Google Play or 👉 learn the opening moves in the Academy.