The Jacoby Rule is one of the most important rule variants in backgammon — and one that fundamentally changes how you value gammons. Named after Oswald Jacoby, the legendary bridge and backgammon player, this rule is standard in most money game play and dramatically affects cube and positional decisions. Understanding it is essential for anyone playing in money games or chouettes.
Key Takeaways
- The Jacoby Rule: gammons and backgammons only count double/triple if the doubling cube has been turned during the game
- Without a cube turn, a win is always a single game — regardless of how many checkers the opponent has borne off
- The rule encourages more cube action and faster, more decisive games in money play
- It significantly reduces the value of gammon threats in certain positions
- The Jacoby Rule is NOT used in match play — only in money games and chouettes where explicitly agreed
- Named after Oswald Jacoby (1902–1984), one of the founders of modern competitive backgammon
What Is the Jacoby Rule?
Under standard backgammon rules, a gammon (opponent has borne off zero checkers) counts as a double win, and a backgammon (opponent has checkers on the bar or in your home board and has borne off zero) counts as a triple win — regardless of whether the doubling cube has been used.
The Jacoby Rule modifies this:
A gammon or backgammon only scores its multiplied value (2× or 3×) if the doubling cube has been turned at least once during the game.
If no one has doubled, the game ends as a single win — even if you’ve born off all your checkers while your opponent has zero off.
Example
| Situation | Without Jacoby Rule | With Jacoby Rule |
|---|---|---|
| You win; opponent has 0 off; no cube turned | Gammon = 2 points | Single win = 1 point |
| You win; opponent has 0 off; cube at 2 | Gammon = 4 points | Gammon = 4 points |
| You win; opponent on bar, 0 off; cube at 4 | Backgammon = 12 points | Backgammon = 12 points |
| You win; opponent has 0 off; cube at 1 (not turned) | Gammon = 2 points | Single win = 1 point |
Why Was the Jacoby Rule Created?
Without the Jacoby Rule, a player in a strong gammon-threatening position has a strategic reason NOT to double — because doubling gives the opponent a chance to pass (take their single-point loss) rather than risk losing a gammon.
This creates a perverse incentive: the stronger player deliberately withholds the cube to extract maximum value, while the weaker player quietly plays on hoping to escape the gammon. Games can become prolonged and dull as the stronger player milks their position.
Oswald Jacoby introduced the rule to fix this: by requiring a cube turn for gammon value, both players have an incentive to use the cube, creating faster, more dynamic games with more cube action.
Effect on Money Game Dynamics
| Without Jacoby Rule | With Jacoby Rule |
|---|---|
| Strong player often waits to double | Strong player must double to claim gammon equity |
| Weaker player waits to see if gammon materialises | Weaker player must decide earlier whether to take or drop |
| Fewer cube turns in gammon-heavy positions | More cube turns overall |
| Games can drag in dominant positions | Games resolve more quickly |
How the Jacoby Rule Affects Your Strategy
Cube Decisions When You Have a Gammon Threat
With the Jacoby Rule, if you’re in a dominant position with strong gammon threats, you must double to preserve the gammon equity. Not doubling means you’ll win only one point even if you win a gammon.
This means the correct play is to double earlier in gammon-threatening positions. Your opponent then faces the full weight of the position including the gammon threat when deciding to take or drop.
Cube Decisions When You’re Behind
If you’re in a losing position and your opponent hasn’t doubled yet (under the Jacoby Rule), you know they cannot win a gammon. This reduces your risk: a pass is not available yet, so you’re at most losing 1 point without a cube turn.
This can make taking slightly worse positions reasonable, knowing the gammon threat isn’t priced in until the cube is turned.
Gammon Price Under Jacoby
The gammon price — how much extra value your gammon threat adds to a position — only kicks in after the cube has been turned. In Jacoby games, the gammon price is zero until someone doubles.
This changes opening strategy: positions that rely heavily on gammon threats (aggressive home board closures, bold blitzes) are slightly devalued under Jacoby, because the gammon equity only becomes real once the cube action begins.
When Does the Jacoby Rule Apply?
| Context | Jacoby Rule Used? |
|---|---|
| Money game (heads-up, agreed) | Yes — standard in most money games |
| Chouette | Yes — usually standard unless agreed otherwise |
| Tournament match play | No — never used in standard match play |
| Casino backgammon | Varies — usually yes |
| Online platforms | Usually toggleable — default varies by platform |
| Home games | By mutual agreement — agree before starting |
Key point: The Jacoby Rule is a money game convention only. It is never used in match play (ABT, USBGF, WBF tournaments), where standard scoring always applies.
Jacoby Rule vs. Other Money Game Rules
Money games often include several optional rules. Here’s how the Jacoby Rule fits alongside others:
| Rule | Effect |
|---|---|
| Jacoby Rule | Gammons/backgammons don’t count unless cube turned |
| Beaver | Player being doubled can immediately redouble and keep the cube |
| Raccoon | Doubler beavers back the beaver |
| Automatic Doubles | Tied opening rolls double the cube (usually capped at 2 or 4) |
| Crawford Rule | Used in match play only — no cube in Crawford game |
These rules are usually negotiated before a session begins. Serious money games typically use the Jacoby Rule and Beavers; Automatic Doubles are optional and less common.
Oswald Jacoby: The Man Behind the Rule
Oswald Jacoby (1902–1984) was one of the most versatile and accomplished card and board game players in history. A world-class bridge player, poker champion, and gin rummy master, Jacoby turned his analytical mind to backgammon in the early 1970s and became one of the leading figures in the backgammon boom of that era.
He co-authored The Backgammon Book (1970) with John Crawford — still considered one of the finest introductory texts ever written on the game. He introduced the Jacoby Rule to speed up money play and make it more strategically interesting, and it was quickly adopted by the international backgammon community.
Frequently Asked Questions
Does the Jacoby Rule apply in online backgammon?
It depends on the platform. Backgammon Galaxy and FIBS both allow the Jacoby Rule to be toggled on or off. Most casual apps do not implement it. Check the platform’s game settings before playing money game sessions.
If I’m clearly winning a gammon, should I always double under the Jacoby Rule?
Yes, in almost every case. The only exception is if you’re so dominant that your opponent will pass at any cube level, in which case you collect a single point. But if there’s any chance they’ll take, doubling is correct — it activates the gammon value.
Can my opponent refuse to play by the Jacoby Rule?
Rules are agreed before a money game session begins. The Jacoby Rule is not universal law — both players must agree to use it. In tournament match play, it never applies.
What happens with Automatic Doubles and Jacoby?
If the cube is already at 2 (from automatic doubles at the start), the Jacoby Rule condition is satisfied — the cube has been “turned.” So gammons count at their full value in that game.
Does the Jacoby Rule affect how often gammons occur?
No — the frequency of gammons in a position is independent of scoring rules. It only affects how gammons are scored, which in turn changes optimal cube and positional strategy.
Further Reading
- Money Game Backgammon — Full guide to money game play
- Gammon & Backgammon — How gammons and backgammons are scored
- Doubling Cube Strategy — Master cube decisions
- Backgammon Chouette — Money game format with multiple players
- Backgammon Books — Including Jacoby’s classic texts