Fu (符) is the unit that measures the structure of a winning hand in riichi mahjong. Every standard hand starts from a 20-fu base (fuutei), then adds points for a value pair, triplets and kan, the wait shape, and how the hand was won. The total is rounded up to the next ten. Chiitoitsu is the exception at a fixed 25 fu.
Simple triplets are worth 2 fu open or 4 concealed; terminal or honor triplets are worth 4 or 8. The corresponding kan are worth 8 or 16 fu for simples, and 16 or 32 for terminals or honors. Kanchan, penchan and tanki add 2 fu; ryanmen and shanpon add none. Under Tenhou rules, a yakuhai pair scores 2 fu for each value, so a double-wind pair scores 4 fu. WRC 2025 limits that double-wind pair to 2 fu.
Pinfu is 20 fu on tsumo and 30 on ron; chiitoitsu is 25 fu. An open ron that would remain at 20 fu is raised to 30. Other totals round up to the next ten. Under WRC 2025, 4 han 30 fu and 3 han 60 fu are kiriage mangan.