Each ability has a modifier that you apply whenever you make a D20 Test with that ability (explained in “D20 Tests”). An ability modifier is derived from its score, as shown in the Ability Modifiers table.
Round Down Whenever you divide or multiply a number in the game, round down if you end up with a fraction, even if the fraction is one-half or greater. Some rules make an exception and tell you to round up.
| 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 |