Spell Attacks vs Spell Saves

Spells that target creatures resolve in one of two ways: the caster makes a spell attack roll, or the target makes a saving throw.

Formula: d20 + spellcasting ability modifier + proficiency bonus.

• Compare the total to the target's AC.
• On a hit, the spell's effects apply. On a miss, they don't (or the spell specifies reduced effects).
• Spell attacks can score critical hits on a natural 20, doubling damage dice.
• Spell attacks suffer disadvantage if a hostile creature is within 5 feet (for ranged spell attacks).
• Spell attacks are affected by cover (target gets +2 or +5 AC from half/three-quarters cover).

Examples: Fire bolt, eldritch blast, guiding bolt, inflict wounds (melee), scorching ray (multiple attack rolls).

Formula: Target rolls d20 + relevant ability modifier (+ proficiency bonus if proficient in that save).

• Compare the total to the caster's spell save DC (8 + spellcasting ability modifier + proficiency bonus).
• On a failed save, the spell's full effects apply. On a success, the spell typically deals half damage or has no effect.
• Spell saves cannot crit — there is no equivalent of a natural 20 on a save for offensive purposes.
• Spell saves are not affected by cover (the target's AC is irrelevant).
• Legendary Resistance allows some powerful monsters to choose to succeed on a failed save (usually 3/day).

Examples: Fireball (DEX save), hold person (WIS save), disintegrate (DEX save, no damage on success), banishment (CHA save).

• Against high-AC, low-save targets: spell saves are more reliable.
• Against low-AC targets or when you want crit potential: spell attacks are better.
• AOE spells almost always use saves. Single-target damage spells use either.