Base attack bonus (BAB) is an attack bonus derived from the character's class levels. See the Class progression table to determine the rate of BAB gained based upon the Class's BAB progression listed in the class description.
Each level taken in a class increases the total BAB of a character by a certain amount.
The base attack bonus increase occurs at different rates for different character classes.
A character gains a second attack per round when his or her base attack bonus reaches +6, a third with a base attack bonus of +11 or higher, and so forth to a maximum of six attacks at +26 BAB.
When an additional attack is gained the attack bonus for this attack is 5 points lower than the previous lowest attack.
Any other modifiers on attack rolls apply to all these attacks normally, but bonuses do not grant extra attacks.
A character with +6 BAB has one attack at +6 and a second attack at +1. When this character reaches +11 BAB, this second attack has reached +6 and gains a 3rd attack with +1. If the same character were to use a +5 sword, the number of attacks still remains the same as the +5 attack bonus from the sword does not count towards number of attacks. Only BAB is used to make that determination.
If a character has multiple attacks this is written with the highest AB (Attack Bonus, the actual BAB plus modifiers) first with a ( slash / ) used to separate each additional attack bonus. ~ also for you to see the number of attacks and the attack bonuses for each consecutive attacks in that Round.
A character with +18 BAB has 4 attacks at +18 / +13 / +8 / +3. If they are using a +3 sword will still ONLY have 4 attacks, but it is listed in the character sheet as +21 / +16 / +11 / +6.
(For calculated full table see Class progression)
|BAB (n)||+ Attack Bonuses / per rounds|
|6-10||+n / +(n-5)|
|11-15||+n / +(n-5) / +(n-10)|
|16-20||+n / +(n-5) / +(n-10) / +(n-15)|
|21-25||+n / +(n-5) / +(n-10) / +(n-15) / +(n-20)|
|26+||+n / +(n-5) / +(n-10) / +(n-15) / +(n-20) / +(n-25)|
Classes are divided into 3 groups based on how their BAB progresses.
BAB=Class level*0.75(rounded down), BAB is gained at 3 out of 4 levels, levels with no gain equal 1+(multiples of 4) (i.e. 1, 5, etc)
BAB=Class level*0.5(rounded down), BAB is gained on every even class level
BAB progression can be seen (along with other class progression information) on the Class progression page.
In MotB, epic levels continue the standard progression. Thus, a Cleric 24 / Fighter 6 would have a medium BAB for 24 levels of Cleric (e.g., +18) plus a high BAB for 6 levels of Fighter (e.g., +6) for a total of +24 BAB. This would result in 5 attacks with a progression of +24 / +19 / +14 / +9 / +4 for the multiclassed character.
When a character multiclasses each class, the BAB progression is based on the class level. Each class provides separate BAB progressions, even if the BAB each class provides is of the same type the progressions do not follow on.
A level 20 Rogue (a medium BAB) has a +15 BAB, while a character with 10 Rogue levels and 10 Monk (also a medium BAB) levels would gain +7 BAB from each class, for a total of +14 BAB at Character Level 20.
Another example could be a character that (for some reason) had 1 level each of warlock, rogue, bard, and druid - all classes with medium BAB progression. Such a character would have a total of + 0 BAB at Level 4 of that Character/Race.