The tables below list the attack probabilities for all monsters and characters and the saving throw values used by monsters and normal humans.

All humans who are not a member of an adventuring class are classified as normal humans. They are treated as having less than 1 Hit Die and have their own saving throw and attack probabilities (the table rows labelled NH).

Occasionally it is necessary to convert values in one Armour Class format to the other. For example, a group using ascending AC might be playing an adventure that only provides descending AC values. To convert between DAC / AAC and THAC0 / attack bonus (AB), simply subtract from 19, as follows:

• DAC to AAC: AAC = 19 – DAC.
• AAC to DAC: DAC = 19 – AAC.
• THAC0 to AB: AB = 19 – THAC0.
• AB to THAC0: THAC0 = 19 – AB.

A 5th level fighter attacks a Fire Beetle (AC 4). The attack is resolved as follows:

1. The player rolls 1d20. The roll comes up 14.
2. The fighter has 13 STR, so gains a +1 bonus to melee attack rolls. The result of the attack roll is thus 15.
3. The fighter has THAC0 17 (listed in the fighter level progression table), so the player refers to the THAC0 17 attack matrix row.
4. The player looks up the attack roll result (15) in the THAC0 17 attack matrix row. 15 is in the AC 2 column, indicating that the attack hits AC 2.
5. As AC 2 is better than the beetle’s Armour Class (4), the attack hits!
6. Damage is rolled and the result subtracted from the Fire Beetle’s current hit point total.

Instead of referring to the attack matrix, attacks can be resolved using THAC0 directly. A THAC0 score denotes the attack roll required to hit AC 0. The attack roll required to hit opponents of other AC scores can be calculated by subtracting the target AC from the THAC0. For example, a character with a THAC0 of 19 could hit an opponent with AC 5 on a roll of 14 or greater (19 – 5 = 14).

Monsters: Use the attack matrix row for their Hit Dice (see monster description).
Monsters with bonus hit points: Monsters whose Hit Dice are notated as a number of dice plus a fixed hit point bonus (e.g. HD 2+1) are more powerful and attack as if they were 1 HD higher. For example, a monster with 2 HD uses the THAC0 18 row, but a monster with 2+1 HD uses the THAC0 17 row.
Characters: Use the attack matrix row for their THAC0 score (see class description).
Normal humans: Use the attack matrix row labelled NH.

Monsters: Use the saving throw table row noted in the monster description.
Characters: Do not use this table. See the saving throw table in the class description.
Normal humans: Use the saving throw table row labelled NH.