Dice Judo Game: Rules, Ippon and Odds
Dice judo is a short, tense match for two players. The players take turns attacking, and every roll of two dice is one attempt at a throw: most grips are broken, some throws score a waza-ari, a rare perfect throw scores ippon and wins at once, and a player who does not attack enough gets a penalty. The scoring follows the real sport closely. You need two dice and a pencil, and a match takes about five minutes. Below are the rules and the exact odds.
What you need
- Two six-sided dice, or a dice roller set to two dice.
- A score sheet with a box for each player’s waza-ari and shido.
- A coin flip to decide who attacks first.
Who attacks first?
The players bow to each other, then toss a coin flip. The winner makes the first attack, and after that the players take turns. Attacking first gives only a tiny edge, as the odds below show.
How to play
- Regular time is 12 rolls: six attacks for each player, taking turns.
- On your attack, roll both dice, add them up and check the chart below.
- Ippon: a roll of 12 is ippon, and you win the match at once. Two waza-ari also add up to ippon and win the match.
- Shido: a roll of 3 or 4 gives you a penalty. A third shido is hansoku-make: you lose the match.
- Time up: after 12 rolls, the player with more waza-ari wins. Shido do not decide the match. If the waza-ari are level, go to golden score: keep taking turns, and the first score of any kind wins. A third shido still loses.
Judo was founded in Japan by Jigoro Kano in 1882 and has been an Olympic sport since 1964. In the real sport, ippon wins at once, a waza-ari can decide a match when time runs out, three shido mean hansoku-make, and a level match goes to golden score. Whether two waza-ari add up to ippon has changed between rule sets over the years, so this game simply uses that rule. Real judo also has pins, holds and armlocks, and its rules change from time to time, so this is a simple home version, not an official game.
The dice chart and the chance of each attack
In the table, “Roll” is the total of the two dice, “What happens” is the result of the attack, and “Chance” is the exact probability out of the 36 ways two dice can land.
| Roll | What happens | Chance |
|---|---|---|
| 2 | Counter: the other player scores a waza-ari | 1 in 36 |
| 3 or 4 | Shido: the attacker gets a penalty for passivity | 5 in 36 |
| 5 to 9 | No score: the grip is broken | 24 in 36 |
| 10 or 11 | Waza-ari: the attacker scores a half point | 5 in 36 |
| 12 | Ippon: a perfect throw, the attacker wins at once | 1 in 36 |
Two attacks in three end with no score, because the middle totals are the most likely, as explained in our guide to dice probability. The attacker scores on 6 rolls in 36 and the other player only on 1, so attacking pays, but a shido comes on 5 rolls in 36.
How is the match won?
In the next table, “How the match is won” is the way the match ends, and “Chance” is the exact probability rounded to whole percent.
| How the match is won | Chance |
|---|---|
| Ippon from a roll of 12 | about 26% |
| Two waza-ari | about 45% |
| More waza-ari when time is up | about 17% |
| Hansoku-make: the other player gets a third shido | about 7% |
| Waza-ari in golden score | about 5% |
Most matches end before time is up: a match lasts about 9.4 rolls on average. About 17% of matches are level after 12 rolls and go to golden score. The player who won the coin flip and attacks first wins about 51% of matches. These numbers are worked out exactly from the rules, not simulated.
Tips
- Bow at the start and end of each match, as judoka do on the mat.
- Mark waza-ari with a tick and shido with a cross so the score is clear.
- For a tournament, draw the pairs with a random name picker and give the winners a gold, silver or bronze medal.
- Call out the Japanese words: “Hajime!” to start and “Soremade!” at the end.
Classroom ideas
- Fractions: in this game two waza-ari make ippon, so pupils can talk about two halves making a whole.
- Probability: why is a roll of 5 to 9 so common? Count the ways, 24 out of 36.
- Languages: learn the Japanese words of judo: ippon, waza-ari, shido, hajime, matte.
- Data: record how each match in a class tournament ended and compare it with the table.
Variations
- Hold-down: after a waza-ari, the scorer rolls one die. On a 6, it becomes a hold-down for ippon.
- Short match: play 8 rolls of regular time for younger players.
- Team match: teams of five, one match each, and the team with more wins takes the round.
- Weight classes: group players by age and draw the pairs within each group.
If you like duels with dice, try dice wrestling next, or cross blades in dice fencing.
FAQ
How do you play judo with dice?
Players take turns attacking. Roll two dice: 12 is ippon and wins, 10 or 11 is a waza-ari, 5 to 9 is no score, 3 or 4 is a shido for the attacker and 2 is a counter that gives the other player a waza-ari.
What is the difference between ippon and waza-ari?
Ippon is a perfect score and wins the match. Waza-ari is a smaller score. In this game, two of them make ippon.
What is a shido?
A small penalty for not attacking. Three shido are hansoku-make, and the player loses.
What is golden score?
Extra time when the score is level after regular time. The first score wins. It is needed in about 17% of dice judo matches.
How long does a dice judo match take?
About 9.4 rolls on average, or a few minutes.
Does attacking first help?
Only a little: the first attacker wins about 51% of matches.