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 |
To determine an ability modifier without consulting the table, subtract 10 from the ability score and then divide the total by 2 (round down).
Because ability modifiers affect almost every attack roll, ability check, and saving throw, ability modifiers come up in play more often than their associated scores.
SRD 5.1 · OGL 1.0a