Gammons in backgammon: how to win one, and how to save one

A gammon is a win in which the loser hasn't borne off a single checker. It counts double. A backgammon is a gammon in which the loser also still has a checker on the bar or in the winner's home board. It counts triple. Every other win is a single game.

Those values are multiplied by the doubling cube: a gammon with the cube on 2 is worth 4 points, a backgammon with the cube on 4 is worth 12. The full scoring rules are in our rules of backgammon.

A win isn't just a win. When you judge a position, the question isn't only “how often do I win?” but also “how often do I win a gammon, and how often do I lose one?” Two positions with the same winning chances can be worth very different amounts if one of them wins many more gammons.

That's what equity measures: the average result of the position in points per game, gammons and backgammons included. An analysis engine weighs every move this way, which is why the best move is sometimes not the one that wins most often.

The simple arithmetic of gammons

In a money game with the cube on 1, the swings are easy to count:

• Turning a single win into a gammon gains 1 point (from +1 to +2).
• Turning a gammon loss into a single loss saves 1 point (from −2 to −1).
• Turning a win into a loss costs 2 points (from +1 to −1).
• Turning a gammon loss into a backgammon loss costs 1 more point (from −2 to −3).

So turning a win into a loss costs twice as much as a gammon gains or saves. A bold play aimed at a gammon pays only if it wins at least about twice as many extra gammons as it adds losses. And a safe play aimed at saving a gammon pays only if it saves at least about twice as many gammons as the wins it gives up. These are rough guides, with the cube on 1 in a money game: the cube and the match score change the weights.

Gammons don't come from luck alone. They come from positions where your opponent has checkers far from home and can't get them back in time. Some positions are naturally gammonish; recognizing them is half the work.

When a gammon is on offer

• Your opponent has several checkers back, on the bar or in your home board, and no anchor to rest on.
• Your home board is strong or getting there: several points made, with builders ready to make more.
• You're attacking: a blitz is the game plan that wins the most gammons (see backgammon blitz).
• A checker is trapped behind a prime while the rest of your opponent's army is still far from home.

How to play for it

• Attack a second checker. One checker on the bar is a threat; two checkers back is often where gammons begin. When your board is strong, hitting a second blot is often worth some risk.
• Close your board. A closed board keeps a checker on the bar for as long as you choose. Every turn it spends there, your opponent's other checkers stay where they are.
• Don't break your board too early. While your opponent still has a checker on the bar or deep in your home board, keep your home points. A board that crumbles lets them escape and get home in time.
• Keep the pressure, not just the lead. When you're far ahead, the easy move is to play safe. If a gammon is still realistic, the move that keeps attacking can be worth more.

Playing for a gammon is not free. Every attacking play leaves something behind: a blot, a broken point, a checker out of play. The arithmetic above gives the rule: a game lost instead of won costs twice what a gammon brings. Stop pushing when:

• Your opponent makes an anchor. With a point to land on in your home board, their checkers are much safer, and your gammon chances usually drop sharply.
• Your attack runs out of builders. Hitting without the checkers to cover or point leaves you exposed to return shots that can turn the game.
• Your opponent bears off a checker. From that moment, no gammon is possible: play the game for the single win, safely.
• The match score says a gammon is worth little, for example when a single win already gives you the match (see gammons in match play).

The opposite mistake is just as costly. Once you've won the game, at least on the board, the only question left is the gammon: there's no reason to play timidly when there's nothing left to lose.

When you're clearly losing, the game changes. Your goal is no longer to win but to bear off one checker before your opponent finishes. That one checker halves your loss, from 2 points to 1 with the cube on 1.

1. Decide early that you're saving the gammon

The longer you wait, the harder it gets. If your winning chances are slim and your opponent is bearing in or bearing off, switch goals now. Hanging on to an anchor in the hope of a late shot can be right, but only if you still have time to come home afterwards.

2. Count crossovers, not just pips

The board has four quarters of six points. A crossover is moving a checker from one quarter to the next. A checker in your opponent's home board needs three crossovers to reach your home board; one on their outer board needs two. Since a single die moves at most six points, each die can make at most one crossover for one checker. Count how many crossovers you need and use every number to make one if you can.

3. Don't waste pips inside your home board

To bear off, all 15 checkers must be home. Moving checkers deep inside your home board brings no checker closer to coming in. Bring your stragglers just inside, usually to your 6-point or 5-point, and keep your big numbers for the checkers still outside.

4. Bear off as soon as you can

Once your last checker is home, take a checker off at the first chance, even if it leaves your board untidy. The gammon is saved the moment that checker is off. The technique of the bear-off itself is in our guide to bearing off.

A backgammon costs you one more point than a gammon, and it only happens when you're stuck: no checker borne off, and at least one still on the bar or in your opponent's home board when they finish.

• Get out of their home board first. When you're losing badly, your first priority is to move your last checkers out of your opponent's home board. Once they're all out, the worst you can lose is a gammon.
• Enter from the bar quickly. A checker on the bar can't move. If your opponent's board is closing, every turn on the bar is a turn of not running.
• Weigh the late shot. Staying back to hit a checker as your opponent bears off can win the game, but it's also exactly how backgammons happen. If you stay, know how many turns you can afford before you must run.

Backgammons are rare compared with gammons, but they cost a full extra point when they happen, and they're often avoidable with a little planning.

Gammons change every cube decision, in both directions. These are the main effects, explained in more detail in our doubling strategy guide:

• Gammons raise the take point. If some of your losses will be gammons, each one costs 4 points instead of 2 after a take. You need more wins to make the take pay, so a position that would be a take without gammons can be a pass (see the take point).
• Gammonish positions can lose their market fast. When a good exchange can turn a strong position into a very strong one, with gammon chances on top, waiting to double can let the position become too strong for your opponent to take.
• Too good to double. If your opponent should pass but you'd win a gammon often enough, doubling cashes 1 point when playing on is worth more. Keep the cube and play for the gammon (see too good to double).
• The Jacoby rule. In money games played under the Jacoby rule, gammons and backgammons count as single wins until the cube has been turned. It doesn't apply in matches.

In a match, the goal is to win the match, not to collect points. So a gammon is worth exactly what it does for your chances of winning the match, and that depends on the score. This is the gammon value. A few situations are worth knowing by heart:

In between those extremes, the value of a gammon rises and falls with the score, and it can be different for each player. The player for whom a gammon counts more can play more boldly; the player who'd lose more from a gammon should be more careful, with the checkers and with the cube. For match structure and Crawford, see backgammon match play; for the cube side, see match play in our doubling guide.

• Playing safe when a gammon is on offer. Far ahead with your opponent on the bar, the cautious move can throw away gammons worth more than the small risk it avoids.
• Chasing a gammon that's gone. Once your opponent has an anchor or a checker off, stop taking risks for a gammon you can no longer win.
• Hanging on too long. Keeping an anchor for a last shot when you can no longer get home in time is a common way to lose a gammon, or a backgammon. When a move raises your risk of losing a gammon too much, Megammon's analysis labels it “Gammon risk underestimated”.
• Burying checkers when saving the gammon. Pips spent deep inside your home board don't bring your last checkers home. Count crossovers instead.
• Doubling out a gammonish position. If your opponent should pass and you'd win a gammon often enough, the double can cost you points. Consider playing on.
• Forgetting the score. In a match, a gammon can be worth nothing, or the whole match. Check what it's worth before you take a risk for one, or to avoid one.

For the classic errors that have nothing to do with gammons, see common beginner mistakes in our rules guide.

Gammon judgment comes from experience: seeing which positions turn into gammons, and feeling when it's time to switch from winning to saving. Every game you play on Megammon, online, against a friend or against the bot, gives you that experience, and you can play the bot with no sign-up.

To measure your progress over all your decisions, gammons included, see how to get better at backgammon. New to the game? Start with the rules of backgammon.