Limit Texas Hold'em

Minimum eligible raise: The raise amount must be at least as much as the previous bet or raise in the same round. As an example, if the first player to act bets $100 then the second player must raise a minimum of $100 (total bet of $200).
Maximum eligible raise: The size of the pot, which is defined as the total of the active pot (which can be either the main pot or the side pot depending on whether anyone has gone “all-in”) plus all bets on the table plus the amount the active player must first call before raising.

As an example, if the active pot is $200 and the first player to act in the round bets $150 and the next player calls $150, the third player has a maximum eligible total bet of $800. The $800 total is made up of the $150 call and $650 raise.
The $650 max raise portion is equal to the pot of $200 + first player's $150 + second player's $150 + his own call of $150.