D&D 5e Spell Save DC Calculator
Work out your spell save DC and spell attack bonus from character level and spellcasting ability — enter either an ability score or a modifier and get both numbers instantly.
Every spellcasting class in D&D 5e uses the same two formulas to set how hard its spells are to resist and how likely its spell attacks are to land. Both numbers come from the same two inputs — your proficiency bonus and your spellcasting ability modifier — so once you know those, the rest is just addition. The calculator below does that addition for you and shows the breakdown; the sections underneath spell out the formula and walk through a worked example.
Spell Save DC & Attack Bonus Calculator
Score 16 → modifier +3
Level 5 → proficiency bonus +3
Spell Save DC
14
Spell Attack Bonus
+6
Spell Save DC = 8 + 3 (prof) + +3 (ability mod) = 14
Spell Attack Bonus = 3 (prof) + +3 (ability mod) = +6
The Formula
Spell Save DC = 8 + proficiency bonus + spellcasting ability modifier
This is the number a target's saving throw has to meet or beat to resist your spell. The 8 is a flat constant that never changes; only the other two terms move.
Spell Attack Bonus = proficiency bonus + spellcasting ability modifier
This is what you add to a d20 roll when a spell calls for an attack roll instead of a saving throw — the same two terms as above, minus the flat 8.
Proficiency bonus by level
| Level | 1-4 | 5-8 | 9-12 | 13-16 | 17-20 |
|---|---|---|---|---|---|
| Bonus | +2 | +3 | +4 | +5 | +6 |
Ability modifier from score
modifier = floor((ability score - 10) / 2)
Round down. A score of 16 gives a +3 modifier; a score of 15 also rounds down to +2.
Worked Example
A 5th-level wizard has an Intelligence score of 16. That score gives a +3 ability modifier, and level 5 puts the wizard in the levels 5-8 band for a +3 proficiency bonus.
Spell Save DC = 8 + 3 (prof) + 3 (INT) = 14
Spell Attack Bonus = 3 (prof) + 3 (INT) = +6
Every target hit by that wizard's fireball has to roll a 14 or higher on their Dexterity save to take half damage, and any spell attack roll the wizard makes adds +6 to the d20.
Frequently Asked Questions
How do you calculate spell save DC in 5e?
Add 8, your proficiency bonus, and the modifier for your spellcasting ability. The base of 8 is fixed for every caster; the other two numbers scale with level and with how high you've built your casting stat.
What is my spell save DC?
Look up your proficiency bonus for your character level (+2 at levels 1-4, rising to +6 at levels 17-20), find the modifier for your spellcasting ability (Intelligence, Wisdom, or Charisma depending on class), and add both to 8. Use the calculator above to get the number instantly instead of doing the math by hand.
How do you calculate spell attack bonus in 5e?
Add your proficiency bonus and your spellcasting ability modifier — there's no flat +8 like there is for spell save DC. That's why your spell attack bonus is always exactly 8 lower than your spell save DC.
Does proficiency bonus affect spell save DC?
Yes. Proficiency bonus is one of the three terms in the spell save DC formula, alongside the flat 8 and your ability modifier. Since proficiency bonus rises with character level (from +2 up to +6), your spell save DC climbs as you level up even if your spellcasting ability score never changes.
Which ability modifier do I use for spell save DC?
Whichever ability your class uses to cast spells — Intelligence for wizards, Wisdom for clerics and druids, or Charisma for bards, sorcerers, paladins, and warlocks. Check your class's spellcasting ability if you're not sure which one to plug into the formula.