In cash games, we have these minimum and maximum buy-ins:
For Fixed Limit games, the minimum buy-in is ten times the big bet. For example, in a $1 or $2 FL game it's $20. There is no maximum buy-in at Fixed Limit tables.
For No Limit and Pot Limit games, the minimum buy-in is 40 times the big blind. The maximum buy-in is 100 times the big blind. For example, in a standard $1 or $2 NL game, the minimum buy-in is $80, and the maximum is $200.
The minimum and maximum buy-ins may differ at some tables. You’ll see a message with any variations when you join the table.