Concentration
A Concentration check is required whenever a spellcaster is disrupted while casting or maintaining a spell. Failure means the spell is lost and the slot is wasted. The check is d20 + caster level + key ability modifier (same ability that sets spell DCs) vs. the situation's DC.
Concentration Check DCs
| Situation | DC |
|---|---|
| Damaged while casting (single hit) | 10 + damage dealt + spell level |
| Taking continuous damage (e.g., on fire) | 10 + ½ last damage + spell level |
| Maintaining a concentration spell after damage | 10 + damage dealt + spell level |
| Cast defensively (avoid provoking AoO) | 15 + 2 × spell level |
| Grappled or pinned | 10 + grappler's CMB result + spell level |
| Vigorous motion (horse at trot, small boat in waves) | 10 + spell level |
| Violent motion (galloping horse, ship in storm) | 15 + spell level |
| Extremely violent motion (earthquake, hurricane-force winds) | 20 + spell level |
| Entangled | 15 + spell level |
| Nondamaging distraction (weather — rain, sleet, hail) | 5 + spell level |
| Distracted by a nondamaging spell (e.g., ghost sound) | Distracting spell's save DC |
"Spell level" in each formula is the level of the spell being cast or maintained — not the slot level used.
Concentration DC Calculator
Failing a Concentration Check
On a failed Concentration check, the spell being cast or maintained is lost and the slot is expended. If maintaining a concentration spell (e.g., wall of fire or black tentacles), the spell simply ends — no additional effect occurs. The caster can attempt to recast on a subsequent turn.