+Healing and +Damage

You may have seen items or effects with statements that say:

"Increases healing done by spells and effects by up to 42."
"Increases damage and healing by spells and effects by up to 42."
"Increases fire damage done by spells and effects by up to 42"

And maybe you wondered "What do these mean?" Well many people assume (wrongly) that the item grants a random bonus between 1 and 42 for each spell cast. But that is not the case, in fact each spell gets a fixed bonus that is mostly determined by the type, casting time, target and / or way the spell is applied.

To determine how much +Healing, +Damage/Healing and +Damage you have you must know that they stack together. If you had two items that each give +20 Nature-damage, one that gives +10 damage/healing, and one that gives +10 healing, your healing spells would have an Advertised Benefit of 20 and your nature-damage spells would have an Advertised Benefit of 30, and all your other damage spells would have an Advertised Benefit of 10.

Formulas for Different Spell Types

The calculations below end in a decimal result that should be less than 1. To get the % multiply that decimal by 100.

First let’s understand the types of spells, as each is calculated differently. There are three base types of spells, these are where your mathmatical calculations begin. The spell is standard, over time or a combination. Then there are other things like Area of Effect and Channeling that then are added to the equation. Then finally in one of the next sections penalties are discussed and added to produce the final answer.

Standard Spell

Standard spells are spells that apply all the damage or healing at one time. The cast time can be anywhere from instant to any number of seconds long.

To determine the plus Healing or Damage benefit for these spells the following formula is used:

Cast Time of Spell / 3.5 =  Benefit 
3.5+ sec = 100%
3.0  sec = 85.71%
2.5  sec = 71.43%
2.0  sec = 57.14%
1.5  sec = 42.86%
Instant  = 42.86%

The Cast Time of Spell should be the base cast time BEFORE talents or gear effects are applied to reduce the casting time. Note that the tooltip in game includes talent effects so use the spell's page on WoWWiki to find the base cast time.

Examples of these spells include: Healing Touch (Druid), Frostbolt (Mage), Greater Heal (Priest), Shadow Bolt (Warlock)

Over Time Spell

Over Time spells apply healing or damage over a period of time in ticks. Ticks can vary from one second apart to three seconds apart. Some spells specify the length of each tick and others require testing to determine.

If a spell has less than five ticks, each tick receives one-fifth of the bonus per tick. If an over time spell has 5 or more ticks, the spell receives full benefit, divided equally between the number of ticks.

(Number of ticks in Spell / 5) =  Benefit 
1  tick  = 20%
2  ticks = 40%
3  ticks = 60%
4  ticks = 80%
5+ ticks = 100% (divided equally between the number of ticks.)

Note that the cap for this calculation is 1 or 100%, more ticks than five will not give you over 100% benefit. +Healing and +Damage benefit for the spell is divided equally to each tick. If talents or gear add more ticks, count the extra tick in your calculations as it may change the benefit.

Examples of these spells include: Rejuvenation (Druid), Renew (Priest), Corruption (Warlock)

Combination - Standard and Over Time Spell

Why are these treated differently? Usually in all other spells discussed the damage or healing is all applied in one way. It may be delivered all at one time or split up into equal parts and distributed over time. With these spells the damage or healing is not divided equally and is applied in two or more different methods.

That Standard portion of the spell does not receive the full benefit because some of the benefit is moved to Over Time portion. So first you need to know what benefit goes to each section of the spell.

Calculation for determining the Portion to the Over Time part of the spell:

(Number of ticks / 5) / ((Number of ticks / 5) + (Cast Time of Spell / 3.5)) = Portion to Over Time 

So to get the Amount to the Regular part of the spell:

1 - Portion to Over Time = Portion to Standard 

Now remember the rules for Standard and Over Time spells still apply. So we have to now consider the cast time of the spell for the Regular part and the number of ticks for the Over Time part.

(Cast Time of Spell / 3.5) * Portion to Standard = Benefit Regular part of the spell 
(Number of ticks / 5) * Portion to Over Time = Benefit Over Time part of the spell

See the notes in the Standard and Over Time spell formula sections to note any definition of terms or explanations on how to determine the Cast Time of Spell or Number of Ticks.

Examples of these spells include: Moonfire (Druid), Immolate (Warlock)

Channeled Spell

Channeled spells have their benefit distributed evenly over the time the effect lasts, getting 100% benefit for the whole spell (not per tick). The duration of the spell cast time is used as with a standard spell to calculate the total benefit, then divided equally between the number of ticks.

Cast Time of Spell / 3.5 =  Benefit 

Examples of these spells include: Hurricane (Druid), Arcane Missiles (Mage), Mind Flay (Priest), Hellfire (Warlock)

Area of Effect Spell

Area of Effect spells receive only 1/3 or 33.3% of the benefit. The cast time is used as with a standard spell to calculate the total benefit, then divided by 3.

(Cast Time of Spell / 3.5) / 3 =  Benefit 
3.5+ sec = 33.33%
3.0  sec = 28.57%
2.5  sec = 23.81%
2.0  sec = 19.05%
1.5  sec = 14.29%
Instant  = 14.29%

Examples of these spells include: Tranquility (Druid), Arcane Explosion (Mage), Prayer of Healing (Priest), Hellfire (Warlock)

Note that some spells fall under the rules for multiple spell types. Hurricane, Tranquility and Hellfire for example are all Area of Effect and Channeled. Prayer of Healing is both a Standard Spell as well as an Area of Effect spell.

Rules for Applying +Healing and +Damage

  1. You calculate spell time using the base spell cast time BEFORE talents and gear reductions to the cast time. (Notice that your casting time in the in-game tool tip will subtract time based on your talents.)
  2. The factor for the casting time is capped at both ends. For the purpose of these formulas, spells that take longer than 3.5 seconds are considered to have 3.5 sec, and spells faster than 1.5 sec are treated like they had 1.5 sec (this is the global cast cooldown).
  3. The number of ticks for a spell is capped at 5 for the purposes of working the equation (but bonus is divided equally between the number of ticks).
  4. Damage benefits are applied before any talents or buffs that may increase your damage by a flat percentile. Healing spells are opposite; all talents are added to the base first then healing benefits added.
  5. Spell criticals are an extra 50% of the original calculated value of the spell after benefits. So if the spell would do 100 damage or healing normally then the critical would be 150.
  6. Gear benefits are added to spells before critical hit modifications are made.

Penalty Rules

Spells learned before level 20

Many spells have multiple ranks. To avoid having players using these lower ranks to deal constant damage at a negligable mana cost, any spell which can be learned at a level lower than 20 has a large penalty applied. If the spell has a shorter cast time, this is also taken in to account. This level penalty can be worked out by taking off 3.75% for each level lower than level 20.

(20 - Level Spell is Learned) * .0375 = Penalty

Additional effects

Spells with additional effects (like slow) get a 5% penalty to benefit. This penalty is applied before other penalties and to the base calculation for the spell. Example a standard spell that is also AOE with an additional slow effect would be calculated:

((Cast Time of Spell / 3.5 ) - .05 Penalty for extra effect) / 3 = Benefit 

Examples of these spells include: Entangling Roots (Druid), Mind Flay (Priest), Blast Wave (Mage)

Spells that do Damage and Healing

Some spells, both damage the target and heal the caster. These spells have a 50% penalty to the bonus they receive, but damage gear increases both the damage and the healing of the spell equally. These spells receive no bonus from gear that only increases healing.

Examples of these spells include: Devouring Plague (Priest), Drain Life (Warlock)

Exceptions to the Rules

  1. Pyroblast was changed in patch 1.9 to deal 100% of +spell damage on impact and 71.4% of +spell damage to it's DoT component. This is currently the only known spell which recieves more than the advertised benefit.
  2. Fireball has a small damage over time component, but is not considered a hybrid spell, so it receives only the Direct Damage bonus to its direct damage component. Spell damage gear never increases the DoT on fireball.

Additional notes

  1. +Damage amount has no effect on chance to crit with spells.
  2. +Healing does not apply to bandages or potions. Trinkets should no longer be affected.
  3. Shaman totems receive benefit from +Damage.
  4. Hunter Traps don't get any benefit from +spell damage.

See also