There are three class BAB increases.
- Main classes: arcane archer, barbarian, blackguard, champion of Torm, dwarven defender, fighter, paladin, purple dragon knight, ranger, and weapon master.
- Second classes: assassin, bard, cleric, dragon disciple, druid, Harper scout, monk*, rogue, shadowdancer and shifter.
*Monks have a special unarmed base attack bonus when fighting unarmed or with a kama.
|Level||Main classes||Second classes||Third classes|
|For levels 21-40 see Epic progression|
BAB and multiclass characters
Calculate the BAB of multiclass characters by adding the BAB of their individual classes. For example, a level 6 barbarian / level 4 rogue adds 6 BAB from 6 barbarian levels with 3 BAB from 4 rogue levels to give +9 total BAB.
Because of this, it is possible to get a very low BAB in early levels from certain combinations such as a monk(2)/cleric(1)/rogue(1), which results in a +1 BAB total. The same character taking all levels in monk would have +3 BAB instead.
BAB and epic characters
Once they reach epic levels, all characters have the same rate of BAB progression, regardless of their class. All epic characters' BAB increases by one every two levels starting at level 21. These epic BAB increases do not add extra attacks.
- Generally speaking, if maximizing the BAB on a character, it is better to take the warrior type classes that use the best BAB progression pre-epic. This yields the highest BAB and most number of attacks. For example, a 20 fighter/20 cleric character that takes 20 fighter pre-epic will have 30 BAB and four attacks whereas if the same character took 20 cleric pre-epic he'll have only 25 BAB and three attacks.
- Gaining multiple extra attacks, such as those gained from haste, rapid shot or divine power, works differently since patch 1.68. When one of these extra attacks is obtained, it is at full BAB, yet every additional extra attack receives a cumulative -5 penalty. For example, a character that has base attacks at 15/10/5 then gains haste and uses rapid shot (-2 penalty), will end up with base attacks of 13/8/3/13/8.