Play Round the Clock Online

What Is Round the Clock?

Round the Clock is the simplest race in the dice cupboard. Each player has a clock face with the numbers 1 to 12 and throws two dice once per turn. You need a 1 to start. If either die shows a 1, tick it off and you now need a 2. A 2 can be a 2 on either die or a 1 + 1. A 5 can be a 5, a 1 + 4 or a 2 + 3. And so it goes, one number at a time, up to the 12, which can only be a 6 + 6. The first player to tick off all twelve numbers in order has gone round the clock and wins.

There are no decisions once the dice land, which is exactly why the game is worth knowing. It can be taught to a five-year-old in one sentence, it is a painless way to learn how two dice add up, and its lopsided second half is the clearest demonstration of two-dice probability in any game. This guide sets out the rules, works through some throws, computes the odds of every number over all 36 throws, and explains how the version on this page plays against the computer.

A Short History of Round the Clock

Nobody has traced Round the Clock to an inventor or a date, and it would be surprising if anyone could. Counting 1 to 12 in order with two dice is the kind of game that gets reinvented at every kitchen table, and the sources that describe it under this name are modern family and school collections of dice games, where it is filed among games for young children who can recognize the spots on a die and count to twelve. Rule sites such as dice-play carry the same two-line description: roll in sequence from 1 up to 12, using either die or the sum, first to 12 wins. Some parents use it to teach the hours on a clock, which is presumably how the name arose.

The name is shared with a darts game. Round the Clock, also called Around the Clock, is a standard darts practice routine in which players hit the numbers 1 to 20 in sequence, and it is far better documented than the dice game. Whether the dice game borrowed the name from the pub oche or the two arose separately from the obvious clock-face image is not known, and it is safer not to guess.

What is clear is the family relationship. Add a third die, allow the sum of any two dice or all three, continue back down from 12 to 1, and let opponents steal the numbers you leave unused, and you have Centennial, also known as Martinetti or Ohio. Round the Clock is that game stripped to the bone.

Round the Clock Rules

Equipment

• Two six-sided dice
• A clock face or list of the numbers 1 to 12 for each player; a sheet of paper is fine
• Something to mark off numbers with, or a counter to move around the clock
• Two or more players; the version on this page is you against the computer

Object of the Game

Make the numbers 1, 2, 3 and so on up to 12 in order, one number per success, before anyone else does.

How a Turn Works

1. Throw both dice once. One throw per turn, then the dice pass to the next player. Some rule sets decide who starts by a high throw; on this page you always throw first.
2. Look for your number. For 1 through 6, your number counts if it shows on either die or if the two dice add up to it. For 7 through 12 only the sum can make it, since no single die goes that high.
3. Tick it off and move on to the next number. You never skip: if you need a 4 and throw 5-6, the throw is wasted even though 5, 6 and 11 are all sitting there.
4. Take a second number if the other die makes it. Under the rule used on this page each die may be counted once per throw, so if you need 3 and throw 3-4, the 3 die makes your 3 and the 4 die makes your 4. Because the sum uses both dice, it can never be combined with a single die, so a throw is worth at most two numbers, and only while you need 1 to 5. The One number per throw toggle switches to the stricter rule of one number per throw.
5. First to 12 wins. The 12 is the last number, and the game ends the moment someone makes it.

Which Throws Make Each Number

Every way to make each number, and how many of the 36 equally likely throws of two dice contain at least one of them. A face appears on at least one die in 11 throws, not 12, because the double (say 3-3) is a single throw.

Worked Examples

• Needing 1, throw 1-2. The 1 die makes your 1, and the 2 die makes your 2. Two numbers from one throw; you now need a 3. Under the strict rule you take the 1 only.
• Needing 1, throw 1-1. You make the 1 with one die. The other 1 cannot make a 2 on its own, and the sum 1 + 1 = 2 would reuse the die you have already counted, so there is no second number. You need a 2.
• Needing 3, throw 3-4. 3 from the 3 die, 4 from the 4 die. This is the double step that makes the first half of the clock go quickly.
• Needing 6, throw 6-1. 6 from the single 6. The 1 does nothing; 7 needs the sum, and the 6 is already spent, so 6 + 1 = 7 is not available. This is why a double step can never carry you past 6.
• Needing 7, throw 2-5. 2 + 5 = 7. Tick it off. From here on, every number needs the sum of both dice and nothing else.
• Needing 12, throw 6-6. Round the clock. This is the only throw that works, one in 36.

The Odds Over 36 Throws

Two dice give 6 × 6 = 36 equally likely ordered throws, and every entry in the table above is a count of them. The pattern splits the clock into two halves.

The first half is easy and gets easier. A given face shows on the first die in 6 throws and on the second in 6, but the double is counted twice, so a specific number appears on at least one die in 6 + 6 − 1 = 11 throws. Sums then add a little more: 1 + 1 gives the 2 one extra throw, 1 + 2 in either order gives the 3 two, and so on. That is why the chance climbs one throw at a time from 11 in 36 for a 1 to 16 in 36 for a 6. Each of the numbers 1 to 6 takes between 2.3 and 3.3 throws on average, and the whole first half takes about 14 throws with double steps allowed, or 16 without them.

The second half is a different game. From 7 upward only the sum counts, and the familiar two-dice pyramid takes over: 6 ways to make 7, then 5, 4, 3, 2 and finally 1 way to make 12. The average wait for a 7 is 6 throws, for a 10 it is 12 throws, for an 11 it is 18, and for a 12 it is 36. The numbers 7 to 12 together take about 88 throws on average, and a solo trip round the whole clock takes about 103 throws under the rule used here, or 104 with the strict one-number rule, which only affects the numbers 1 to 5.

The 12 is a coin that almost never lands. Waiting for a 6-6 has no memory: the chance is 1 in 36 on every throw, however long you have waited. The median wait is 25 throws, meaning half of all players are still waiting after their twenty-fifth try. After 50 throws, 24.5% of players are still waiting; after 100 throws, 6.0% are. In a two-player game the finish is nearly always a duel of 6-6 attempts, and reaching 12 first is only a modest edge.

Double steps are rare. Needing any of 1 to 5, exactly 2 of the 36 throws (5.6%) contain your number on one die and the next number on the other. It is worth a cheer, but it saves a throw or two over the game, not more.

Round the Clock Strategy

Once the dice are thrown there is nothing to decide in Round the Clock, so the tips below are about running the game well: reading throws, teaching with it, and shaping it to the table.

1. Read the single dice first, then the sum

For 1 to 6, glance at each die for your number before you add. Players who add first miss the single: needing a 4 with a throw of 4-5, the 4 is right there and 9 is irrelevant. For 7 and above only the sum matters.

2. Look for the second number before you pass the dice

If you need 1 to 5 and made your number with one die, check the other die for the next number. A throw of 2-3 when you need 2 is a 2 and a 3. Under the rule used here the second step is only ever a single die, never a sum, so there is nothing else to check.

3. Teach the first half as an addition drill

For a child, the numbers 1 to 6 are where the learning is. Ask “which ways can you make a 5?” and let them find the 5, the 1 + 4 and the 2 + 3 themselves. Once they see that the 6 has more ways than the 1, they have understood why the chance climbs, without a single formula.

4. Teach the second half with the table

From 7 up, the question becomes “why does 12 take so long?” Lay out all 36 throws on paper, or point to the Chance per Throw table beside the game, and count: six ways to make 7, one way to make 12. The same pyramid runs Craps, Chicago and Shut the Box, and Round the Clock is the gentlest place to meet it.

5. Expect the wait and do not read anything into it

The 12 arrives on 1 throw in 36 regardless of what came before. A run of twenty misses does not make the next throw more likely to succeed, and a player who has been stuck for ages is not “due.” Say so out loud when children play; it is the most useful thing the game teaches.

6. Use the strict rule to slow things down, not to add skill

The One number per throw toggle removes the double step. It makes each turn simpler to check, which suits very young players, and lengthens the game by about two throws per player. It adds no decisions either way.

7. Shorten the game when you need to

A full clock is long for a small child’s attention span. Agree beforehand to stop at 6, to race to 9, or to declare whoever is furthest ahead after a set number of rounds the winner. The first half already contains most of the fun.

8. Move up when it gets stale

When the family can read two dice at a glance, Centennial adds a third die, a return trip and the stealing rule, which is where the game grows some teeth. For a two-dice game with real choices, Pig is the natural next step.

Common Mistakes

• Adding when you do not need to. Needing a 3 with a throw of 3-6 and calling it a 9.
• Using a die twice. Needing 6 with a throw of 6-1 and claiming the 6 and then the 7 from 6 + 1. The 6 has been counted; the 1 on its own is not a 7.
• Skipping ahead. Needing a 4 and taking a 5 because it is sitting there. The numbers must come in order.
• Taking two numbers from a sum. Needing 3 with a throw of 1-2: the sum makes the 3, but it uses both dice, so there is no die left for a 4.
• Believing the 12 is overdue. It never is; the chance is 1 in 36 on every throw.

Variants and House Rules

• One number per throw. Every throw is worth at most one number, even when the second die shows the next one. Most short rule descriptions mention only one number per throw, so this is probably how many families play; it is available here via the One number per throw toggle.
• Sum only above 6. Some descriptions spell out that from 7 upward only the sum counts. That is not a different rule, just a consequence of the dice, and the game on this page behaves exactly this way.
• High throw starts. Some rule sets have each player throw once and the highest total starts. On this page you always throw first, and the computer takes the second turn.
• Three dice, up and back. Add a third die, allow the sum of any two or all three, return from 12 down to 1, and let opponents steal unused numbers. That is Centennial, which has its own guide.
• Shortened clocks. Racing to 6 or to 9 keeps the game to a few minutes for young children; the wait for the 12 is the long part.

Glossary

• Clock: A player’s list of the numbers 1 to 12, usually drawn as a clock face; the last number is 12.
• Needed number: The next number a player must make; shown in the center of each clock on this page.
• Single: Making the needed number with one die on its own; possible only for 1 to 6.
• Sum: Making the needed number by adding both dice; the only way to make 7 to 12.
• Double step: Making two consecutive numbers from one throw with separate dice, possible while needing 1 to 5.
• Strict rule: At most one number per throw (“one number per throw”).
• Round the clock: Having made all twelve numbers; the game ends immediately.

Play Round the Clock Online on Dice.now

The game at the top of this page is a race between you and the computer. Each of you has a clock face with the numbers 1 to 12 arranged like the hours; numbers you have made are filled in, the number you need next is marked and shown in the center of your clock, and a number you have just made is highlighted. The status bar shows what each side needs, whose turn it is, and your win-loss record on this device.

Press Roll Two Dice to take your turn. You get one throw, and the game reads it for you: your needed number is taken if it shows on either die or if the two dice add up to it, and if the other die then shows the next number, that is taken too. Each die is counted once, so a sum and a single are never combined, and a throw is worth at most two numbers. The counted dice light up, the message line says which numbers were ticked off, and the game log keeps the last 40 events. After a short pause the computer rolls under exactly the same rules; it has no decisions to make and no advantage.

The One number per throw chip switches to the strict rule, under which every throw is worth at most one number. You can toggle it between throws, the change is noted in the log, and it applies from the next throw. The Chance per Throw panel beside the game lists, for each number from 1 to 12, how many of the 36 throws make it and the percentage, so you can watch the odds fall as you climb. When someone makes the 12 the game ends, an overlay tells you what the loser was still waiting for, and your record is saved only in your browser. Ready to go round? Roll two dice.