A game played with a spread-limit betting structure allows a player to raise any amount within a specified maximum (subject to other betting rules).
For example, a game with a “$1000 spread-limit” allows each player to call and then raise up to a maximum of $1000.
A simpler approach is to bet up to a maximum amount equal to the spread-limit. So in the above example, the maximum bet (call + raise) is limited to $1000.
In a game played with a fixed-limit betting structure, the maximum raise amount generally equals the last bet amount (current level of bet). Thus, the maximum raise amount is equal to the call amount, and the maximum bet is double that of the last bet.
A game played with a pot-limit betting structure allows any player to raise up to an amount equal to the size of the whole pot before the raise.
For example, let us assume that there is an ante of $50 and a single forced blind bet of $10 in the pot at the start of the regular betting round, and all subsequent players are seen/have seen their cards. The next player may bet the minimum amount of $20 (double that of the last blind bet of $10). This player may also raise up to $80 (as there is now $50 + $10 + $20 = $80 in the pot) to bring his total bet (also the new current level of bet) to $20 + $80 = $100. If he does in fact bets $100, the total amount of the pot is $160, and the next player may call (put the minimum bet of) $100, and raise up to $260 for a total bet of $360 (after calling the $100 bet, the total amount of the pot is $260, so he may raise up to $260). The next player would then be entitled to call at $360 and raise up to $880 (after calling $360, the pot would contain $880, thus he may raise $880).
A simpler approach is to bet up to a maximum amount in the pot. So in the above example, the first seen player may bet a minimum of $20 and a maximum of $60. If he does bet the maximum, the next player may bet a minimum of $60 to a maximum of $120. If he bets the maximum, the next player would then be entitled to bet a minimum of $120 and a maximum of $240.
Note: In this example, for the later bets, the maximum bet is twice that of minimum bet because of the chosen ante and forced blind bet amounts. For other combinations, this relationship may not hold.