Fu

Fu is the secondary scoring axis in Japanese Riichi, a count of small points awarded for the structural details of a winning hand. While han measures the value of named patterns, fu measures how the hand is built: the type of sets, the wait shape, the pair, and the manner of winning. Fu and han are then combined to produce the final score, with fu mattering most at lower han counts.

Fu accrues from a base of 20 points for any hand, plus 10 for a concealed ron win (menzen kafu) and 2 for a self-draw (except in pinfu). Triplets add fu by tile type and concealment: a concealed triplet of simples is 4 fu, of terminals or honors 8 fu, with open triplets and kan worth more or less accordingly, and a concealed kan of honors reaching 32 fu. The pair adds 2 fu if it is a value tile (dragons or the relevant winds), and the wait adds 2 fu for an edge, closed, or pair wait.

The total is then rounded up to the nearest 10. Two special cases bend the rules: pinfu, an all-runs hand with no fu-bearing elements, is fixed at 20 fu (or 30 on a ron), and chiitoitsu (seven pairs) is fixed at 25 fu. These fixed values keep otherwise fu-less hands from scoring zero structural points.

Fu can quietly change a hand's bracket. A 30 fu and 40 fu hand at the same han count often score differently, and at 4 han a high fu total can reach mangan via the rounding tables. Fu is purely a Riichi mechanic; Chinese, Hong Kong, and Taiwanese variants have no equivalent and score entirely from their fan, faan, or tai pattern values. For example, a concealed ron with a terminal triplet, a closed wait, and a dragon pair totals 20 + 10 + 8 + 2 + 2 = 42, rounded up to 50 fu.