Combat rating system

Patch 2.0.1 introduced a new mechanic: combat ratings. These ratings are for combat stats (on items) that were previously percentage-based. Such as: critical strike chance, hit chance, dodge chance and defense skill. They were introduced because percentage based itemization would have scaled excessively when The Burning Crusade was released and the player cap rose to 70.

Combat Rating types

The following combat ratings are currently in use:

Armor penetration rating Block rating Critical strike rating Defense rating Dodge rating

Expertise rating Haste rating Hit rating Parry rating Resilience rating

Deprecated Spell hit rating Spell critical strike rating Spell haste rating Weapon skill rating

Combat skills

See also: Critical strike, Spell critical strike

Unlike fixed percentages such as 2% critical strike chance, combat ratings diminish in potency as your character increases in level. 2% crit is the same at every level, while 28 critical strike rating grants 4% crit at level 34, 2% crit at level 60, and 1.27% crit at level 70. This allows Blizzard the ability to create and add new and better items to the world without eventually reaching a point where every character has a 100% chance to critically strike.

Below are the conversion for level 60, level 70, and level 80 combat skills:

Rating	Effect	Requires
		Level 60	Level 70	Level 80
Expertise	-1% Dodge/Parry	10	15.77	32.79
Melee Hit	1% hit chance	10	15.77	32.79
Spell Hit	1% spell hit chance	8	12.62	26.23
Critical Strike	1% critical strike chance	14	22.08	45.91
Haste	1% haste	10	15.77	32.79
Armor Penetration	1% armor ignored	4.70	7.40	15.40

Prior to patch 2.0.1, Weapon Skill reduced the percentage of damage lost due to glancing blows.

Between patch 2.0.1 and patch 2.3, Weapon Skill gave player +0.1% to their critical strike rating per weapon skill against monsters above their level.

As of patch 2.3, all items which previously had Weapon Skill Rating or Feral Combat Rating now have an equal amount of Expertise Rating.

From the 2.3 PTR patch notes: "We have added a new stat and associated rating called expertise and expertise rating. Expertise rating converts to expertise at the same rate that weapon skill rating formerly converted at. Each point of expertise reduces the chance for your attacks to be dodged or parried by 0.25%."

Unlike Weapon/Feral Combat Rating, Expertise does not have diminishing returns beyond 20 rating. For players, this means that once the hit cap has been reached, one can begin stacking Expertise to increase damage potential against mobs with high dodge/parry. Melee DPS classes won't benefit much from the -parry (as they should be behind the target), however dodges do make up a considerable chunk of lost damage. Druid tanking items with Expertise, such as Earthwarden, will be more valuable for consistent threat generation since a parried/dodged Mangle can be devastating.

Since Expertise is 'capped' by the target's chance to dodge/parry, the ideal rating varies per mob. The average level 73 boss has a 6.5% chance to dodge. Completely negating a 6.5% chance to dodge would require 102 Expertise rating at level 70, assuming the character had no talents which reduced his target's dodge chance.

Defense skills

The impact on the defense skill system is slightly more complicated. This skill actually grants a percentage-based benefit already; every 25 points of defense skill grants a 1% dodge chance, 1% parry chance, 1% block chance, 1% increased chance to be missed and 1% decreased chance to be critically hit by physical attacks.

Below are the defense rating values needed to achieve 1% of each effect:

Rating	Effect	Requires
		Level 60	Level 70	Level 80
Defense Skill	1 defense skill	1.5	2.37	4.92
Defense Skill	1% combined miss/dodge/parry/block	9.375	14.8125	30.75
Defense Skill	1% combined miss/dodge/parry	12.5	19.75	41
Dodge	1% dodge	12	18.92	39.35
Parry*	1% parry	15	23.65	49.18
Block	1% block chance	5	7.88	16.39

• Parry was changed in the 2.1 patch to require 25% less rating to equal 1% Parry. The old value at 70 was 31.54 rating for 1%.

All of these Ratings have the same "point cost" when determining the level of an item. (See the article on Item values for an in-depth discussion.) For comparison, 1 point of Block Value, which decreases the damage taken when a block occurs by 1, costs 0.65 as much as 1 point of any of these Ratings.

Resilience

See also: Resilience

Resilience reduces the effects of all types of critical hits (both physical and spell crits from players or mobs). Resilience has three components; it reduces the chance you will be critically hit by x%, and it reduces the damage dealt to you by crits that land by 2x% and finally damage taken from DoTs is reduced by x%. x is the percentage resilience granted by a given resilience rating. In 2.4 an additional effect was added to resilience. It reduces the amount of mana drained or burned by mana draining effects by 2x%.

PvE tanks usually have high enough +defense values so that mobs won't crit them at all, thus in PvE this is not an important statistic for warriors, but for druids this is another story, see note below. Template:Resilience Note: For feral tanking druids, resilience can be more useful than defense to reach crit immunity, 2.6% crit to overcome at lvl 70 with Survival of the Fittest. This is no longer true as of patch 3.0, where druids can become crit immune though SotF alone, without defense or resillience. The formulas are still valid if you don't have 3/3 of this talent.

60 defense rating = (-1%crit,+1%miss,+1%dodge,+1%parry,+1%block)
39.4 resilience rating = (-1%crit,-2%crit damage)
14.7 agi = (+1%dodge,+0.58%crit,+29.4 armor)

The conclusion is that if your goal is to become a crit-immune druid, you can swap 60 defense rating for 39.4 resilience rating + 29.4 agi. This is because (1%miss and 1%dodge) = 2%dodge, see also Attack Table for this. So this tradeoff gives you the same crit immunity and gives even slightly better damage mitigation because of the use of Agility. This trade-off is also good for the extra crit and armor, which are both useful for feral tanks. Looking at normal stats of defense rating and resilience on armor and weapons, it is easier to get crit immunity through resilience than through defense. This is not true for Warriors and Paladins as they can Block and Parry and therefore get much more benefit from defense rating than feral druids.

Leveling

Each time you go up a level, the amount of rating needed to get the same benefit will increase. An example of the scaling involved would be the current implementation of Agility which has always worked this way in the live game, requiring more agility for the same critical strike chance as you go up in level.

Diminishing returns

As of Patch 3.0.1, combat ratings that affect avoidance stats now have diminishing returns. See Formula:Diminishing returns for the exact details.

Combat Ratings formula

See also: Melee mitigation

The following formulas give the amount of rating required to achieve a 1% bonus. They can be derived from two sources, the values stored in the client and extensive testing done by the author of the Rating Buster addon, and are completely accurate (each method gives the same values within the margin of error for 32-bit floating point precision, or 10^-7).

Values are calculated with below formulas:

File:Ratings graph.jpg

Ratings Conversion Graph

Resilience,Hit,Crititical Strike, Haste,Expertise,Armor Penetration		Dodge (Patch 2.1), Defense,Parry,Block (Patch 2.4.2)
LEVEL	FORMULA	LEVEL	FORMULA
1-10	$\frac{base}{26}$	1-34	$\frac{base}{2}$
10-60	$base\frac{level-8}{52}$	34-60	$base\frac{level-8}{52}$
60-70	$base\frac{82}{262-3level}$	60-70	$base\frac{82}{262-3level}$
70-80	$base\frac{82}{52}\left(\frac{131}{63}\right)^\frac{level-70}{10}$	70-80	$base\frac{82}{52}\left(\frac{131}{63}\right)^\frac{level-70}{10}$

The 70-to-80 formula may change in future patches, but is current as of Patch 3.0.3.9183 (verified Dec 2, 2008).

Rating	Combat variable	Base (value at lvl 60)
Armor Penetration	- % of target's armor	3.756097412
Block	+ % block chance	5
Critical Strike	+ % melee crit chance	14
	+ % ranged crit chance
	+ % spell crit chance
Defense	+ defense skill	1.5
Dodge	+ % dodge chance	12
Expertise	+ melee weapon skill	2.5
Haste	- melee weapon speed׆	10
	- ranged weapon speed×
	- cast time
Hit	- % melee miss chance	10
	- % ranged miss chance
	- % spell miss chance	8
Parry	+ % parry chance	15
Resilience	- % chance to recieve melee crit	25
	- % chance to recieve ranged crit
	- % chance to recieve spell crit
	- % melee crit dmg taken	11.36363636
	- % ranged crit dmg taken
	- % spell crit dmg taken
	- % DoT dmg taken	25
	- % mana drained	11.36363636

×) "-" is here because the variable that Blizzard calls speed is actually the period between two swings/shoots. Actual speed is increased.

†) Paladins, Shamans, Druids and Death Knights receive 30% extra value for this stat (effective base value is 13)

Ratings calculators

Ingame

• Rating Buster, an addon which shows and calculates Combat ratings on your items (Curse | WoWInt).

Excel

Simply enter your current stat ratings and level in the appropriate cells, and all the math is done for you.

Ratings Calculator

Historical note

Prior to version 2.0.1, item bonuses didn't use the Combat Ratings System. Instead, items had equip and on-use bonuses that increased the underlying value directly. For example, instead of increasing the wearer's Crit Rating by 14 and the wearer's Dodge Rating by 12, the old pre-2.0.1  [Stormshroud Shoulders] added +1% to the wearer's Crit chance and +1% to the wearer's Dodge chance.

When Blizzard made the conversion to 2.0.1, all existing items with the old +crit%, +defense, etc. values were converted to their equivalent values in the new Ratings system scaled for a level 60 character. For example, an item that previously gave +10 Defense Skill now gives +15 Defense Rating. (Conversions that would have resulted in a fractional Rating were rounded down to the nearest whole number; e.g. an item that previously gave +3 Defense Skill now gives +4 Defense Rating.)

See also

• Formulas:Item Values
• Attack table

References

Combat Rating System Explanation | 2006-10-17 01:06 by Eyonix

Combat Ratings: Level 70 Conversions | 2006-10-20 18:29 by Eyonix

Combat Ratings: Level 70 Conversions | 2007-05-30 18:23 by Eyonix

Blizzard BETA Combat Rating System Notes | 2006-12-09 14:46 by Drysc

Blizzard Combat Rating Conversion Factor at 70 | 2007-05-30 18:23 by Eyonix