Ability Scores

Six abilities provide a quick description of every creature's physical and mental characteristics:

Is a character muscle-bound and insightful? Brilliant and charming? Nimble and hardy? Ability scores define these qualities--a creature's assets as well as weaknesses. The three main rolls of the game--the ability check, the saving throw, and the attack roll--rely on the six ability scores. The book's introduction describes the basic rule behind these rolls: roll a d20, add an ability modifier derived from one of the six ability scores, and compare the total to a target number.

Ability Scores and Modifiers

Each of a creature's abilities has a score, a number that defines the magnitude of that ability. An ability score is not just a measure of innate capabilities, but also encompasses a creature's training and competence in activities related to that ability.
A score of 10 or 11 is the normal human average, but adventurers and many monsters are a cut above average in most abilities. A score of 18 is the highest that a person usually reaches. Adventurers can have scores as high as 20, and monsters and divine beings can have scores as high as 30.
Each ability also has a modifier, derived from the score and ranging from -5 (for an ability score of 1) to +10 (for a score of 30). The Ability Scores and Modifiers table notes the ability modifiers for the range of possible ability scores, from 1 to 30.

Score Modifier
1 -5
2-3 -4
4-5 -3
6-7 -2
8-9 -1
10-11 +0
12-13 +1
14-15 +2
16-17 +3
18-19 +4
20-21 +5
22-23 +6
24-25 +7
26-27 +8
28-29 +9
30 +10