Spellcasting & Concentration Helper

Calculate Pathfinder 1e spell save DCs, concentration checks and caster-level checks against spell resistance. Keep the target’s saving throw separate from your own casting checks.

PATHFINDER 1E

01 · Your caster & spell

Use your current score and caster level for this spell, including relevant adjustments. Spell level means its effective level for your class, including Heighten Spell. Other metamagic and using a higher slot do not increase this level. Other modifiers are totals after stacking; exclude feats selected below.

Combat Casting (+4 defensively / grappled)

Spell save DC

TARGET'S SAVE

Spell allows a saving throw

The target rolls its save; you set the DC. A natural 1 fails and a natural 20 succeeds.

Cast defensively

CONCENTRATION

Success avoids attacks of opportunity for casting. Failure loses the spell. Other interruptions can still require separate checks.

Concentration

INTERRUPTION

Spell resistance

CASTER LEVEL

Spell resistance applies and is active

Meeting SR is enough. This check does not add your casting ability modifier. Check once per creature per casting.

Rules & scope

Concentration and caster-level checks have no automatic failure on 1 or success on 20. The displayed chance assumes one ordinary d20 roll.
Concentration is caster level + casting ability modifier. Combat Casting applies to defensive casting and casting while grappled, including pinned; it does not apply to ordinary injury checks.
Continuous damage uses half the damage last dealt, rounded down. A damaging spell uses the injury situation; a non-damaging distraction uses the disrupting spell's save DC (or the DC it would have).
While grappled or pinned, you can cast only spells without somatic components and with any material components already in hand. Passing this check does not remove those restrictions.
Choose Spell Focus only when its school matches this spell. The +2 choice includes both Spell Focus and Greater Spell Focus. The +4 penetration choice includes both Spell Penetration feats.
Maintaining a concentration-duration spell normally takes a standard action; you cannot cast another spell while concentrating on it. Interruptions can also break maintained concentration. This helper calculates checks, not action economy or spell eligibility.
Use Custom concentration DC for a specific rule or magical weather. Spell-like abilities, psychic casting, arcane spell failure, components, class prerequisites and special rerolls are not automated.

Inputs stay on this page and reset on reload. Rules checked 1 October 2026.

Choose the correct check

Spell save DC = 10 + spell level + casting ability modifier + applicable DC bonuses: the target rolls against it. Concentration = caster level + casting ability modifier + applicable check bonuses: you roll against the displayed interruption DC. Defensive casting uses concentration against DC 15 + twice spell level. Spell resistance uses d20 + caster level + applicable penetration bonuses against SR, without the casting ability modifier.