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**Spirit-based regeneration **

The main base stat which regenerates mana is spirit. To a lesser extent, intellect also contributes, and the character level adversely affects regeneration. It’s a good rule of thumb to assume that 1 spi = 1 mp5 while not casting.

MP5 = 5 * (0.001 + sqrt(Int) * Spirit * Base_Regen) *rounded up*

Base Regen lvl 80: 0.005575

Chart

The above chart was generated using this data. The formula shows that regeneration increases linearly with spirit and with the square root of intellect. The base regeneration goes down as level increases. When analyzing the plot it appears that levels 1-10 have one curve, 11-60 another and 61-70 have a jagged but almost linear decrease which seems to have been tweaked by hand.

Together these design elements seem to enforce balanced stats, so that stacking spirit to the detriment of intellect is to be avoided. It seems that 1 spirit = 1 MP5 was the target of the game designers. A level 70 caster needs about 460 intellect to reach this point.

**Five Second Rule**

After a character expends mana in casting a spell, the effective amount of mana gained per tick from spirit-based regeneration is reduced (*interrupted*) for a period of 5 seconds. This is commonly referred to as the **five second rule** (**FSR**).

Channeled spells are handled a little differently. The FSR starts when the spell’s channeling starts; i.e. when mana is expended. The interruption continues for at least five seconds, and longer if the channeled takes more than five seconds. For example, Mind Flay channels for 3 seconds and interrupts regeneration for 5 seconds (from the moment the spell cast starts), while Tranquility channels for 10 seconds and interrupts regeneration for the full 10 seconds, but not longer.

By default, the interrupted mana regeneration ratio is 0%. Several effects can increase this ratio, including:

Spells which don’t cost mana do not start the FSR. This includes spells with a normal mana cost of zero (e.g. Nature’s Swiftness), but also spells whose effective cost is reduced to zero by some effect (e.g. by Clearcasting or an item ability or proc like Eye of Gruul).

Effect |
Interrupted mana regeneration ratio increase |

Innervate |
100% (and increases mana regeneration to 500%) |

**Direct regeneration**

Many effects increase mana regeneration directly i.e. without increasing spirit. These effects are governed by different rules than spirit-based regeneration, in particular they’re never subject to the five second rule.

The most frequent source of non-spirit-based regeneration is the “regenerates X mana in 5 seconds” stat on items. This stat is usually written abbreviated as “mp5”.

**Comparing spirit based and direct regeneration**

In theory, direct regeneration is preferable as it is not subject to the FSR. Unfortunately though, mp5 is much harder to get and more “expensive” than spirit. All attributes have an Item Value, a kind of “cost” associated. This value for mp5 is 2.5 times higher than for spirit. For example the two top mana regeneration enchants for chest items yield either 15 spirit or 6 mp5 ([Enchant Chest – Major Spirit] and [Enchant Chest – Restore Mana Prime]) – this shows the factor of 2.5 very clearly.

In order to find out what’s better, characters should first find out their personal time spent inside the FSR, e.g using an addon like Muse or RegenFu. It’s important to perform the measurement under realistic conditions – the time spent inside the FSR while grinding is typically much lower than during a boss fight. Some players actually argue that in a tight situation, it’s safe to assume that the FSR is in effect 100% of the time. It is possible to calculate the percentage of time which has to be spent outside the 5 second rule so that 2.5 points of spirit are more effective than 1 point of mp5. Examples:

Average lvl 70 priest with maxed Meditation: 2.5 spirit return 2.5 mp5 outside the FSR, and 0.75 mp5 inside. The mathematical form of the question is thus

2.5 * x + 0.75 * (1 - x) = 1
1.75 * x = 0.25
x = 0.14

So if that priest spends 14% percent of the time outside the FSR, the enchant with 15 spirit yields a higher regeneration than 6 mp5. If the time inside the rule is 86% or more, 6 mp5 is more efficient.

For lvl 70 characters without spirit regeneration inside the FSR:

2.5 * x = 1
x = 0.4

That is they have to spend 40% of their time outside the rule for spirit to be better than mp5.

**MP5 vs Intellect and Spirit – Formulas**

The following formulas relate intellect, spirit, and mp5 to mana regen both in and out of FSR in an attempt to help establish a relative value between them depending on your current stats.

Based on the formulas for spirit-based regeneration above…

ManaRegen(Int,Spirit,MP5) = [0.001 + sqrt(Int) * Spirit * 0.005575] * 5 + MP5 ManaRegenCasting(Int,Spirit,MP5) = [0.001 + sqrt(Int) * Spirit * 0.005575] * 5 * Coeff + MP5 where Coeff is the decimal percentage of spirit-based mana regeneration that is allowed to continue while casting

The mana regen benefit per 1 point increase of Spirit, Intellect, or Mana/5 can be calculated as…

While not casting:
NC_RegenPerInt = 0.027875 * Spirit * [sqrt(Int+1) - sqrt(Int)]
NC_RegenPerSpirit = 0.027875 * sqrt(Int)
NC_RegenPerMP5 = 1
While casting:
C_RegenPerInt = Coeff * NC_RegenPerInt
C_RegenPerSpirit = Coeff * NC_RegenPerSpirit
C_RegenPerMP5 = 1

As you can see, MP5 is the only stat whose effect remains constant both in and out of casting. If you have no talents allowing mana to regenerate from spirit while casting, MP5 is the only way to do so. Even with them, MP5 is still quite valuable, given the most common of these effects (listed above) cap at 30% spirit-based regeneration.

Multiple ratios do stack, but can never exceed 100%.

**Formula**

Research by Whitetooth^{[1]} shows that since Patch 2.4, mana regeneration is uniform across all classes and based on the following formula:

Mana Regen = 5 * sqrt(Int) * Spirit * Base_Regen In effect, the regeneration rate depends on Int, Spirit and character level. A 1% increase in Spirit increases mana regeneration by 1%, and 1% Intellect yields 0.5% more regen. This is a rough rule of thumb, but is accurate enough for most situations. Intellect doesn’t influence mana regen linearly, rather the square root of Intellect is used. This means that higher Int values yield diminishing returns, as can be seen in the following table:

`Intellect vs Spirit Coefficient`