How many dominoes are in a set?

Guides · Updated 1 October 2026

A standard double-six set has 28 dominoes: every possible pairing of the numbers blank to six, each appearing exactly once. Larger sets follow the same rule. A double-nine set has 55 dominoes, a double-twelve set has 91, a double-fifteen has 136 and a double-eighteen has 190.

That answers the question. The rest of this page explains why those particular numbers come out, and which of the numbers inside a set actually change how you play.

How many dominoes are in each set size

Why a double-six set has 28 dominoes

A domino set is a list of every way to pair up its numbers, with no pair repeated. A double-six set runs from blank to six, which is seven numbers, and the count breaks into two parts.

First the doubles, where a number is paired with itself. There is one for each number, so seven of them:

Then the singles, where two different numbers share a tile. Seven numbers can be paired seven times six ways, but that counts every tile twice (a 6–4 and a 4–6 are the same domino), so halve it: 21. Seven doubles plus 21 singles make 28.

The same reasoning works for any set. If the highest number is n, the set has n + 1 numbers, and the total is:

tiles = (n + 1) × (n + 2) ÷ 2

For a double-six, that is 7 × 8 ÷ 2 = 28. For a double-twelve, 13 × 14 ÷ 2 = 91. Each step up in size adds one more number, and that number has to be paired with every number already in the set plus itself, which is why the sets grow so much faster than their names do.

How many dominoes are in a double-nine set?

A double-nine set has 55 dominoes: ten doubles from double-blank to double-nine, and 45 singles. It is the set for Chicken Foot and the natural choice when you have more players than a double-six can deal a full hand to.

How many dominoes are in a double-twelve set?

A double-twelve set has 91 dominoes: thirteen doubles and 78 singles. It is the standard set for Mexican Train, and the thirteen doubles are exactly why that game runs thirteen rounds, one per double, counting down from twelve to blank.

The numbers that matter when you play

Tile counts are trivia. These are not.

Each number appears on seven tiles

In a double-six set, every number turns up on exactly seven dominoes. Here are the seven that carry a six:

This is the single most useful fact in dominoes. Players call the tiles sharing a number a suit, and because every suit has seven members, you can count them. If six of the seven sixes are on the table or in your hand, you know exactly where the seventh is: with your opponent, or out of play. A number with no tiles left can never be answered again, and leaving it on an open end shuts that end for good. The strategy guide builds most of its advice on this.

The whole set holds 168 pips, and the average tile is a six

Add the spots on all 28 tiles and you get 168. Divide by 28 and the average tile carries exactly six pips. That is not a coincidence of the double-six set: in every set, the average tile carries the set’s own number. A double-nine averages nine pips a tile, a double-twelve twelve.

It gives you a quick way to judge a hand. Seven tiles from a double-six set average 42 pips, so a hand totalling 30 is light and one totalling 55 is heavy. That matters because scoring counts pips: in a blocked game the lightest hand wins, and the winner of any round scores what the loser is still holding.

You will usually hold one or two doubles

Seven of the 28 tiles are doubles, so a seven-tile hand holds 1.75 of them on average. The exact odds for a single hand are worth knowing:

• no doubles at all: 9.8% of hands;
• three or more doubles: 22.0% of hands.

More than one hand in five, then, starts with three doubles or worse, and that is bad news: a double can only ever be played against one number, which makes it the hardest tile in the set to get rid of. In 20,000 simulated games, a player holding three or more doubles who did not lead won only about a third of the time. The full figures are in dominoes statistics.

With two players, half the set is never seen

A two-player deal hands out 14 tiles and leaves 14 face down. In Block dominoes those 14 are never played at all, which is why the game blocks so often: numbers run out while their tiles sit unseen at the side of the table. The chance that neither player is dealt a single double is about 1 in 345, which is why the rule that the highest double leads almost always has a double to work with.

Which domino set should you buy?

Buy a double-six first. It plays Block, Draw, All Fives, Fives and Threes, Matador and Texas 42, and it is the set every other size is an extension of. Add a double-twelve if you regularly have five or more people round a table, because Mexican Train is the best of the big-group games and it needs one. A double-nine sits in between and is the one to get if Chicken Foot is your game. The larger sets are for serious Mexican Train players and collectors.

If you are not sure which game you will end up playing, the guide to the types of domino games lists the set each one needs.

Is it “dominos” or “dominoes”?

Dominoes is the standard plural, the one rule books and players use, and it takes an e like potatoes and heroes. Some American dictionaries accept “dominos” as a variant, but you will rarely see it in print.