Mahjong: Luck vs Skill, Through the Lens of Probability

Deal luck, decision skill

Your opening 13 tiles are random, but every draw and discard is a decision under uncertainty. Strong players win more over many hands even though any single hand can be decided by one unlucky tile.

Think of mahjong like poker: the cards dealt are luck, but folding, attacking and reading opponents are skills that compound over hundreds of hands.

Tile efficiency is measurable

Hands with many dual-purpose waits reach tenpai faster. Shanten counting (how many steps your hand is from ready) is the core of efficiency. Playing to lower shanten on every turn is the fastest beginner improvement.

This site shows your tenpai status and lets you compare discards against the AI, so you can see which choices keep the hand efficient.

Reading the table

Discards reveal intent: a player suddenly discarding honors is likely tenpai. Late-game, the safest tiles are genbutsu (their discards) and suuji. Defense converts a losing position into a non-losing one (the highest-leverage skill in riichi).

The numbers behind the luck

You see 13 of 136 tiles and the discards (roughly 20% of the wall). The chance your next draw is one of your waits is about 3-4% per tile, so a hand reaches tenpai within a few turns only with good shape. This is why efficiency beats hoping: a dual wait doubles your odds.

Statistically, strong players win 30-35% of their games at a full table instead of 25% (a modest edge per hand that compounds into domination over hundreds of games).

Deliberate practice

Improve fastest by isolating one skill: ten games where you only count shanten after every draw; ten where you only track your waits; ten where you fold every riichi you are not ready to beat. This site's Easy AI lets you practice counting without pressure, and the sidebar shows your tenpai state live.

Review after each game (the settlement dialog lists your wins and losses). A player who reviews ten hands learns more than one who plays fifty on autopilot.