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Calcimator

Spell Damage Calculator

Calculate average, expected, and critical spell damage factoring in save DCs and spell level efficiency.

Inputs

Results

Expected Damage

21.7

Average (No Save)28
Maximum Damage48
Minimum Damage8
Save Failure Rate55%
Damage per Slot Level7.23
Critical Hit Damage56
Base Dice8
How to Use This Calculator
  1. Enter the damage dice count and select the die type (d4–d12) the spell uses.
  2. Add any flat damage modifier and set the spell slot level (0 for cantrips).
  3. Set your spell save DC and the target's saving throw bonus, and choose whether the spell deals half damage on a successful save.
  4. Review the Expected Damage, which factors in the target's save failure chance, alongside the Average, Maximum, and Minimum Damage.
  5. Compare the Damage per Slot Level and Critical Hit Damage outputs to evaluate spell efficiency.

How the result changes with Damage Dice Count

Damage Dice CountExpected Damage
2.97.87
7.6520.75
1335.26
1848.83

What each input means

Damage Dice Count
Number of damage dice (e.g. 8 for Fireball's 8d6).
Die Type
Type of damage die.
Damage Modifier
Flat damage bonus (many spells have +0).
Spell Slot Level
Level of the spell slot used (0 for cantrips).
Your Save DC
Your spell save DC (8 + proficiency + ability mod).
Target's Save Bonus
Target's saving throw modifier.
Half Damage on Save
Whether the spell deals half damage on a successful save.

What each result means

Expected Damage
Average damage accounting for save probability.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Damage Dice Count = 8, Die Type = 6, Damage Modifier = 0, Spell Slot Level = 3 = 7 input(s) provided
  2. Calculate Expected Damage
    Expected Damage
    21.7 = 21.7
  3. Calculate Average
    Average
    28 = 28
  4. Calculate Maximum Damage
    Maximum Damage
    48 = 48

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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