A size bonus or penalty depends on a creature's size category. Size modifiers apply to Armor Class, attack rolls, Hide checks, grapple checks, as well as some others.
Size modifier to attack and AC
| Fine | Diminutive | Tiny | Small | Medium | Large | Huge | Gargantuan | Colossal |
| +8 | +4 | +2 | +1 | +0 | -1 | -2 | -4 | -8 |
Grapple size modifier
| Fine | Diminutive | Tiny | Small | Medium | Large | Huge | Gargantuan | Colossal |
| -16 | -12 | -8 | -4 | +0 | +4 | +8 | +12 | +16 |
Hide size modifier
| Fine | Diminutive | Tiny | Small | Medium | Large | Huge | Gargantuan | Colossal |
| +16 | +12 | +8 | +4 | +0 | -4 | -8 | -12 | -16 |