Doubling Cubes

Q: What is a doubling cube?

A doubling cube is a six-sided die marked 2, 4, 8, 16, 32, 64 that tracks the current stake multiplier in a backgammon game. It is the single most important rule innovation in modern backgammon, introduced in New York in the late 1920s. The full mechanics are on the rules page section on cube play; the strategic mathematics are on the match equity page.

Q: Where does the doubling cube sit on the board?

At the start of the game, in the middle of the board, on top of the bar, showing 64. When a player offers a double, they turn the cube to 2 and place it on their opponent's side of the board. If the opponent takes, the cube stays on their side; they now own it.

Q: Who invented the doubling cube?

The doubling cube was introduced anonymously in a Manhattan club between 1925 and 1928. The consensus attribution to "an unknown New York player, c. 1925" is supported by Oswald Jacoby and John Crawford in their The Backgammon Book (1970). The full origin story is on the backgammon history page.

Q: How heavy should a doubling cube be?

Tournament-grade cubes weigh 20–40 grams depending on size. Cheap plastic cubes feel insubstantial in the hand (under 10g); collector editions with brass cores can exceed 60g. The weight matters: turning the cube is a meaningful gesture in the game, and a substantial cube reinforces that.

Q: What's the standard size for a tournament doubling cube?

22–25mm on each side. Large enough to read clearly across a 21-inch board; small enough to sit on the bar without overhanging. Collector editions sometimes run larger (28–30mm) but begin to crowd the bar in active play.

Q: What happens to the doubling cube in the Crawford game?

The cube is removed from play entirely for the Crawford game (the single game after one player reaches a score of match-length minus one). Many players physically take the cube off the board for that game. The cube returns for all subsequent post-Crawford games. Full treatment of the Crawford rule and its strategic implications is on the Crawford rule page. ---

The doubling cube is the single most important rule innovation in modern backgammon. Introduced in a Manhattan club between 1925 and 1928 (see the history page for the full origin story), it transformed backgammon from a folk race game into a piece of formal decision theory. Every modern equity calculation, every match equity table value, every world-championship-level cube action depends on this one six-sided die marked 2, 4, 8, 16, 32, 64.

GamesGrid sells tournament-grade doubling cubes under our own brand — both standard tournament weight and collector editions for cube enthusiasts. This page covers what makes a great doubling cube, the anatomy of the standard 2/4/8/16/32/64 numbering, the weight and material choices, and the current GamesGrid selection.

1. What makes a great doubling cube

A doubling cube is the most-handled single object in a serious backgammon match. The cube starts in the middle of the board, gets turned, moves between players, gets turned again, and over a long tournament weekend might be physically picked up and rotated a hundred times. The qualities that matter:

Weight

A great doubling cube has weight. A cheap cube is hollow plastic and feels insubstantial in the hand; a tournament-grade cube is solid (typically acrylic, methacrylate, or in heavier examples, brass-cored) and has the heft that makes the act of turning the cube feel like a real decision. The standard tournament weight is 20–40 grams depending on cube size; collector editions can run 60 grams or more.

The weight matters psychologically as much as ergonomically. Offering a substantial cube is a different physical gesture from sliding a piece of light plastic across the board. Players who play seriously gravitate toward heavier cubes for this reason.

Size

The standard competition cube is 22–25mm on each side — large enough to read the current value clearly across a 21-inch board, small enough to sit comfortably on the bar (the central raised divider) without overhanging. Collector editions sometimes run larger (28–32mm); these are striking objects but they begin to crowd the bar in active play.

Number clarity

The 2/4/8/16/32/64 numbers should be engraved or inlaid rather than painted or stickered. Painted numbers wear off; inlaid numbers (etched into the cube and filled with contrasting material) last indefinitely. The standard treatment is white inlay on black cube or black inlay on white/cream cube; some collector editions use gold inlay for premium aesthetic.

The number must be unambiguously readable. A cube where the numerals are decorative-script rather than standard-numeric makes for slow reading in the middle of a match. We list only cubes with clean, standard numerals.

Material

Three material categories dominate the tournament-grade cube market:

Cellulose acetate / methacrylate — the standard casino-quality material. Holds inlay cleanly, doesn't yellow with age, available in transparent or solid colours.
Brass-cored cubes — a brass core wrapped in cellulose acetate. Heavier and more substantial in hand than pure acetate. Collector-tier.
Solid brass or bronze — premium collector editions. Maximum weight, distinctive sound when set on the board, develops patina over time.

2. Cube anatomy — what each number means

The doubling cube's six faces show 2, 4, 8, 16, 32, 64 — a geometric progression. The cube starts the game at a value of 1 (no face is marked 1; instead the cube sits in the middle, face up, typically showing the 64 by convention, with the implicit value being 1× the current stake).

When either player offers a double, they turn the cube to 2 and push it to the opponent. The opponent takes (accepting the new 2× stake) or drops (conceding the current game at the current 1× stake). If taken, the cube is now owned by the opponent — only they can offer the next escalation. Each escalation doubles: 2 → 4 → 8 → 16 → 32 → 64. The 64 face is the upper limit only because the cube has six faces; in extended or money play, players sometimes track higher values by writing the implied multiplier on the board.

The full mechanics of cube action, take points, double points, and the formal mathematics are on the match equity page. For competitive use, every player should also understand the Crawford rule (which removes the cube from a specific Crawford-game match position) and the Jacoby rule (a money-play rule that affects when gammons count).

3. The standard cube placement

The cube starts the game in the middle of the board, on top of the bar, showing the 64 face up. This is the convention that signals "value is currently 1, cube available to either player." When a player offers a double, they turn the cube to 2, place it on their opponent's side of the board (not back to the middle), and announce the double.

If the opponent takes, the cube stays on their side; they own it. If the opponent drops, the cube returns to the middle showing 64 (value back to 1) and the new game begins.

In post-Crawford games, the trailing player typically doubles at first opportunity. In the Crawford game itself the cube is removed from play entirely — many players physically take the cube off the board to make this visible.

4. The GamesGrid cube selection

We offer GamesGrid-branded doubling cubes in two tiers:

Tournament tier

Standard 22–25mm acetate cubes with inlaid numerals, in matched pairs (one for each player, kept at table for visibility) or singles. The everyday cube for serious club and tournament play. Brand-marked with a discreet GamesGrid monogram on one face.

Collector tier

Brass-cored or solid-bronze cubes in larger sizes (28–30mm), with gold or silver inlay numerals. These are presentation pieces as much as playing pieces — they sit well on a luxury board, develop patina over time, and serve as memorable competition prizes for club tournament organisers. Limited editions appear periodically and are listed here as they're released.

The cube selection opens at GamesGrid launch. Sign up to be notified.

Frequently asked questions about doubling cubes

What is a doubling cube?

A doubling cube is a six-sided die marked 2, 4, 8, 16, 32, 64 that tracks the current stake multiplier in a backgammon game. It is the single most important rule innovation in modern backgammon, introduced in New York in the late 1920s. The full mechanics are on the rules page section on cube play; the strategic mathematics are on the match equity page.

What does the 64 mean on a doubling cube?

The 64 face is shown up at the start of the game by convention, but the implicit cube value is 1 (no face is marked 1). Each time the cube is turned, the value doubles: 2 → 4 → 8 → 16 → 32 → 64. The 64 face is the upper limit only because the cube has six faces; some money-play formats track higher values informally.

Where does the doubling cube sit on the board?

At the start of the game, in the middle of the board, on top of the bar, showing 64. When a player offers a double, they turn the cube to 2 and place it on their opponent's side of the board. If the opponent takes, the cube stays on their side; they now own it.

Who invented the doubling cube?

The doubling cube was introduced anonymously in a Manhattan club between 1925 and 1928. The consensus attribution to "an unknown New York player, c. 1925" is supported by Oswald Jacoby and John Crawford in their The Backgammon Book (1970). The full origin story is on the backgammon history page.

How heavy should a doubling cube be?

Tournament-grade cubes weigh 20–40 grams depending on size. Cheap plastic cubes feel insubstantial in the hand (under 10g); collector editions with brass cores can exceed 60g. The weight matters: turning the cube is a meaningful gesture in the game, and a substantial cube reinforces that.

What's the standard size for a tournament doubling cube?

22–25mm on each side. Large enough to read clearly across a 21-inch board; small enough to sit on the bar without overhanging. Collector editions sometimes run larger (28–30mm) but begin to crowd the bar in active play.

Do I need a doubling cube for casual play?

If you're playing cubeless backgammon, no — the cube is only used when cube play is in effect. But most serious play uses the cube, and even casual club play benefits from including it. A GamesGrid tournament cube costs roughly what a meal out does and lasts decades.

What happens to the doubling cube in the Crawford game?

The cube is removed from play entirely for the Crawford game (the single game after one player reaches a score of match-length minus one). Many players physically take the cube off the board for that game. The cube returns for all subsequent post-Crawford games. Full treatment of the Crawford rule and its strategic implications is on the Crawford rule page.