Backgammon doubling strategy: when to double, take or pass

A checker-play error usually costs a small slice of a game. A cube error can cost a whole one: pass a double you should have taken and you give up a game you were still fighting for; take one you should have passed and you risk twice the stake. That's why tournament players and the analysis of every serious match report cube errors separately from checker play.

If you're new to the cube itself, start with the doubling cube rules: how to offer a double, what taking and passing mean, and who owns the cube afterwards. This guide is about the next question: when to use it.

Start with the receiver, because the doubler's decisions depend on it. When you're doubled with the cube at 1, you choose between two outcomes:

• Pass: you lose 1 point, for sure.
• Take: you play on for 2 points. You lose 2 when you lose and win 2 when you win.

Suppose you win one game in four. Over four such games, taking gives you one win of 2 and three losses of 2: a net loss of 4 points, the same as passing four times. So in a money game, leaving gammons aside, 25% winning chances is the break-even point: above it, take; below it, pass. This is the take point.

Two things move it. Owning the cube lowers it a little, because after taking you're the only one who can double, and you can use that to cash out a game that turns your way (cube ownership). Gammons raise it: if some of your losses will be gammons, each one costs 4 points instead of 2, so you need more wins to make the take pay. Your own gammon chances work the other way: they lower it.

You can't double whenever you're ahead. Double too early and you hand your opponent the cube, and the right to redouble, for a small edge. Double too late and your opponent simply passes, and you collect 1 point from a position that was worth more. The right moment sits between two limits, the doubling window:

• The lower limit: you're a clear favorite, and your position can still improve sharply on the next exchange.
• The upper limit: your opponent's chances have fallen below their take point. Now they should pass: if gammons are unlikely, you double and they drop; if gammons are likely, see too good to double.

Strong players don't decide from a percentage alone. They ask three questions about the position:

• Am I clearly the favorite? Count the race, compare the boards, look at who has blots and who has anchors.
• Can I lose my market? A market loser is a sequence, a good roll for you followed by a bad reply, after which your opponent would pass. If many sequences do that, double now, while they can still take.
• What happens when things go wrong? If your good rolls win big but your bad rolls leave you only slightly worse, doubling costs little. If one bad exchange would leave you the underdog with your opponent owning the cube, doubling is costly: wait.

Sometimes your position is so strong that doubling is a mistake. If your opponent would rightly pass, doubling wins you exactly 1 point. But if you'd also win a gammon often enough, playing on with the cube in the middle is worth more than 1 point on average. That position is too good to double.

Typical too-good positions: you're attacking with several checkers on the bar or in your home board, your opponent has no anchor, and you have builders ready to close points. A simple rule of thumb: if you'd win a gammon more often than you'd lose the game, keep the cube and play on.

Keep checking every turn. A too-good position can turn into a double-and-pass after one bad roll, when your gammon chances drop. That's the moment to double and cash.

How to win those gammons, and how to save one when you're on the other side: see gammons in backgammon.

Once contact is broken and the game is a pure race, cube decisions depend mostly on the pip count: how many pips each side still has to move (how to count them). A widely used rule of thumb for long races, with the leader on roll:

• Double when you lead by about 8% of your pip count.
• Redouble when you lead by about 9%.
• Your opponent should pass when you lead by more than about 12%.

Example: you're on roll with 100 pips against 109. Your lead of 9 pips is 9% of 100, so you have a double, even a redouble, and your opponent still has a take. At 100 against 114, a 14% lead, they should pass.

The percentages are an approximation. They work best for long races, roughly 80 pips or more each, with smooth positions. Gaps on your home board or stacked checkers waste pips, so count them as a few pips more than the raw total. Short races follow their own rules, and bear-offs are best checked with an engine; for the checker play itself, see bearing off fast and safely.

Everything above is money-game theory. In a match, the score changes what each game is worth, so the take point and the doubling window move, sometimes a lot (see backgammon match play for structure and Crawford; short rules on the rules page). A few situations come up all the time:

• The Crawford game is played without the cube: no decisions to make.
• After Crawford, the leader needs one point and owning the cube is worth nothing to them, so the trailer should almost always double (post-Crawford).
• At double match point, both players need one point and the cube plays no part.
• When the gammons count differently for each side, the player who gains more from a gammon can play more boldly, and the one who'd lose more should take and double more carefully.

Players handle the score with a match equity table, which gives each player's chance of winning the match from any score. You don't need to memorize one to start: play the money rules above, and use the special cases in this list.

Getting ready for a live event? Formats, the clock and over-the-board rules are in our guide to backgammon tournaments.

• Passing too often. The most common error. If you win one game in four, taking is right, and many positions are better than they look.
• Doubling too late. Waiting for a sure thing means your opponent passes and you lose your market. Double when the next exchange could make you too strong.
• Doubling too early. A small edge in a quiet position doesn't justify giving up the cube.
• Forgetting gammons. They raise the take point for the receiver and can make the doubler's position too good to double.
• Doubling out a gammonish position. If your opponent should pass and you'd win a gammon very often, consider playing on (see too good).
• Ignoring the score. In a match, a correct money decision can be a clear mistake at the actual score.

For the other classic errors, from stacking checkers to running blindly, see common beginner mistakes in our rules guide. And if your first move is still a guess, start with the best backgammon opening moves, then read the 5 game plans that follow it.

Cube skill grows from feedback: you make a decision, then find out whether it was right. Three habits help:

• Decide before you roll. At the start of every turn, ask whether it's time to double. Most missed doubles are doubles nobody thought about.
• Ask the take question out loud. When doubled, ask: do I win at least one game in four, and how many of my losses are gammons?
• Review your cube errors on their own. They're fewer than checker errors but often bigger, so they're the fastest points to win back.

What your PR means, what a good one is and how to bring it down: see how to get better at backgammon.