To make effective characters and evaluate threats, you have to understand how D&D works. This post explains the basic concepts behind 4e.


The Basic Attack Bonus (BAB) is the key number to hit things. It’s your permanent to-hit bonus that you use for your main attacks. It’s the main number you add to your attack roll. The basic BAB forumula is:

BAB = Ability Mod + 1/2 level + weapon proficiency

The Warrior BAB: 6-8

The Warrior classes use martial weapons such as swords or bows to hit things. A typical martial BAB is 6-8.

1st level Warlord:

  • Strength 18 = +4
  • 1/2 level = +0
  • BattleAxe Proficiency = +2

The Warlord’s BAB is +6. By using a proficiency +3 weapon, and 20 strength, it can go up to +8.

The Caster BAB: 4-5

Martial weapons have proficiency bonuses, implements do not. Casters use implements, so lose the bonus. A typical caster BAB is 4-5.

1st level Warlock:

  • Charisma 18 mod = +4
  • 1/2 level = +0

The Warlock’s BAB is +4.

Casters BAB lags 2-3 points behind Warriors, and this trend continues as characters level. This seems unfair, but we’ll see how it evens out.

The 55% rule

DnD uses the “55% rule.” That a properly-leveled character, on average, has a 55% chance to hit a monster of the same level. In other words, hit on a die roll of 10 or better. That’s supposed to apply as a general rule across the game. It drives creature design. Let’s see how.

A level 1 Kobold Skirmisher has these defenses: AC 15, FORT 11, REF 14, WILL 13.

Warriors usually attack AC, so a character with BAB +6 will hit the monster (AC 15) on a die roll of 9, or 60% of the time. Skirmishers are lightly armored, so that feels right.

Casters on the other hand, almost target the non-AC defenses (NADs): Fortitude, Reflexes, or Will. Note that the skirmisher’s NADs are lower than AC.

A caster with BAB (+4) has these chances to hit:

  • FORT – 7+ = 70%
  • REF – 10+ = 55%
  • WILL – 9+ = 45%

Casters, on average, hit at 57% across all three NADs. The actual hit chance depends on the spell chosen.

This pattern holds for most monsters in the game. Even though casters have lower BAB, they they ave the luxury of attacking lower defenses. Thus all classes can achieve about 55% hit rate.

The difference between warriors and casters

Now look at a level 1 Dire Rat: AC 15, FORT 15, REF 13, WILL 11.

The Kobold Skirmisher’s FORT was his weakest NAD, but that is the Rat’s strongest NAD. But the AC stayed the same.

This is the key difference between warriors and casters. Warriors tend to attack AC, and AC doesn’t vary too much across monsters. Warrior don’t switch weapons very often. Instead, they worry about how land good hits: positioning, flanks, opportunity attacks, etc.

Casters DO switch spells, because the NADs vary for every monster. Casters worry about choosing a good mix of spells to target different NADs, and then figuring out what a creature’s weakness is on the battlefield. They don’t worry about gritty details like flanking, because they are usually blasting away from range.

Extra credit: defenses by monster role

This is important info for casters: in general, you can guess about a creature’s defenses if know the monster role (soldier, brute, etc.).

There are the average defenses of all creatures, by role, at level 1:

           Artillery   Brute   Controller   Lurker   Minion   Skirmisher   Soldier
AC                15      14           15       14       14           15        17
Fortitude         13      15           14       11       13           14        16
Reflex            13      11           12       12       11           14        13
Will              12      11           13       10       10           12        13


  • Fortitude is the strongest NAD overall.
  • Reflex is the middle NAD overall.
  • Will is the weakest NAD overall.

If you have to guess, prioritize this way:
Artillery (bows) – WILL, FORT, REF
Controller – REF, WILL, FORT
Lurker – WILL, FORT, REF
Minion – WILL, REF, FORT
Skirmisher – WILL, REF or FORT (tie)
Soldier – WILL or REF (tie), FORT


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