Fan and payment
A hand is worth base × 2^fan. With a base of ten, three fan is 80 and eight fan is 2560 — every extra fan doubles the money, which is why most tables cap fan somewhere around eight or ten.
On a self-draw all three players pay one share each and the winner collects three. A discard has two common rules: the discarder pays alone, or the discarder covers all three shares. Pick whichever your table uses in settings.
Nobody wants to do 2^8 in their head
Big hands are where the mental arithmetic breaks down. A base of ten at eight fan is 2560, and four people at the table will produce four different answers — that is where the arguments start. Tap the hand types and the number appears, along with who owes whom.
If a hand type is missing from the list, the extra-fan stepper underneath takes whatever your table has agreed on. Set the cap to your house rule and anything above it counts as the cap.
Common questions
How is this different from riichi?
Cantonese mahjong has no fu, no riichi sticks and no honba — the money follows straight from the fan count, which is far simpler. For Japanese rules pick the Riichi Mahjong entry instead.