The Doubling Cube: When to Double and When to Take
The doubling cube is the reason backgammon is a game of skill and not just a dice race. Used well, it wins you points in games you would have won anyway, and saves you points in games you were going to lose. This guide covers the three questions every player asks: when should I double, when should I take, and when should I pass?
If you’re new to the cube, our rules page explains how it works. In short: before you roll, you can offer to double the stakes. Your opponent either takes, and the game carries on for twice as much, or passes, and loses the game straight away at the current stake.
The take point: why 25% is the magic number
Start with the decision your opponent faces, because it decides everything else.
Say the game is worth 1 point and you double to 2. If your opponent passes, they lose 1 point. If they take, they play on for 2 points. Taking is worth it if, on average, they lose less than 1 point by playing on.
Here’s the sum. If they win the game a quarter of the time:
- 1 game in 4 they win 2 points
- 3 games in 4 they lose 2 points
- over 4 games that’s +2 −6 = −4, or −1 point a game
So at exactly 25% winning chances, taking and passing cost the same. With more than 25%, take. With less, pass. That 25% is called the take point.
In real games it’s a little lower than 25%, because the player who takes owns the cube and can redouble later if the game turns. Many players use something nearer 20 to 22% as a working figure. Gammons push it the other way: if you might lose a gammon, which costs double, you need better chances to take.
When to double
The best moment to double is when your opponent still has a take, but only just. That’s when you gain the most: they’re playing on for twice the stake with poor chances.
Signs it’s time to double:
- You’re clearly ahead, and things could change fast. If your next roll or two could leave your opponent with no take at all, double now. This is called doubling before you lose your market.
- You have a strong threat. For example, your opponent has a checker on the bar against your strong home board, or you’re one roll away from closing them out.
- You’re well ahead in the race. See the race rule below.
Signs you’re doubling too early:
- The game is close and could go either way.
- Your advantage is real but slow, and nothing much will change in the next few rolls.
When you’re too good to double
This surprises a lot of players. Sometimes you should not double because you’re winning by too much.
If you have a strong chance of winning a gammon (worth 2 points with the cube in the middle), doubling lets your opponent pass and lose just 1 point. That throws away your gammon chances. When you’re attacking hard and your opponent has several checkers back, it’s often better to keep playing for the gammon and only double once the gammon chances have mostly gone.
A simple rule for races: 8, 9, 12
Once all contact is over, the game is a pure race, and the decision comes down to the pip count. If you haven’t counted pips before, our guide on how to count pips shows you how.
For races where the leader has more than about 100 pips left, a widely used rule of thumb, often credited to the backgammon writer Walter Trice, goes like this. Work out your lead as a percentage of your own pip count, then:
- Double if you lead by 8% or more
- Redouble if you lead by 9% or more
- Your opponent should take if your lead is 12% or less, and pass if it’s more
Example: you need 120 pips and your opponent needs 132. Your lead is 12 pips, which is 10% of 120. That’s a double, and with a lead of 12% or less, it’s a take.
The rule assumes it’s your turn to roll. In shorter races the percentages change, and experts use more detailed counts, but 8, 9, 12 is a good start.
When to take
Your opponent has doubled. Ask yourself:
- Do I win at least one game in four from here? If yes, lean towards taking.
- Could I lose a gammon? If you have several checkers back and your opponent’s board is strong, you need better winning chances to take.
- Will owning the cube help me? If the game could turn, owning the cube means you can redouble and make your opponent face the same choice.
A useful habit: when you’re unsure, picture playing the position out four times. If you’d expect to win one of them, take.
Common mistakes with the cube
- Doubling when it feels good, not when the position is right. A strong position isn’t always a doubling position. Ask whether your opponent still has a take.
- Passing too often. New players pass far too many doubles. Backgammon has a lot of luck in it, and 25% is a lower bar than it feels.
- Taking when a gammon is likely. Losing 4 points at the cube on 2 hurts much more than passing for 1.
- Forgetting the cube at all. Many games are lost by playing on for 1 point when a well-timed double would have ended them early.
Practise the ideas
Our game plays single games without the cube, so it’s a good place to work on the skill behind cube decisions: judging who is really ahead. During a game, pause now and then and ask yourself, “Would I double here? Would I take?” Then see how the game turns out.
For the rest of the rules, including the Crawford rule in match play, see the backgammon rules. For the ideas that get you into strong positions in the first place, read our strategy guide.