Combat rating system

Combat rating system is a mechanic introduced in patch 2.0.1 which are for secondary stats on items that were previously percentage-based. Rating is converted linearly to percentage; the number of rating points needed to gain one percentage point increases with level and varies depending on the stat, but is the same for all classes. Combat ratings were introduced because percentage-based itemization would have scaled excessively when The Burning Crusade was released and the level cap rose to 70.
==Secondary ratings==
The following secondary ratings are currently in use:
* Avoidance rating
* Critical strike rating
* Dodge rating
* Haste rating
* Mastery rating
* Leech rating
* Parry rating
* Speed rating
* Versatility rating
Unlike fixed percentages such as 2% critical strike chance, combat ratings diminish in potency as characters increase in level. 2% critical strike chance is the same at every level, while 14 critical strike rating grants 5.16% crit at level 10, 2.62% crit at level 30, and 0.4% crit at level 60. 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. Combat ratings further diminish as a player gains excessive stats from rating, reducing the rating's potency even at the same player level.
All classes convert ratings into attributes at the same ratio, with the exception of Mastery, where the ratio is determined by class specialization. Below are the conversions for combat ratings at various levels:
===Combat Ratings===
The following table shows the amount of rating necessary for 1% of a secondary stat before diminishing returns. Due to the nature of this change, the exact rating values for diminished stats will not be listed.
Rating 	Effect 	Level 10	Level 25 	Level 50 	Level 60 	Level 70 	 	 	 	
Critical strike	1% critical strike chance 	2.71 	4.59 	10.67 	35 	180 	 	 	 	
Haste 	1% haste 	2.55 	4.34 	10.06 	33 	170 	 	 	 	
Mastery 	1% Mastery 	 	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information	Varies by specialization - See Mastery for more information
Versatility 	1% Damage/Healing and 0.5% Incoming Damage Reduction	3.09 	5.25 	20 	40 	205 	 	 	 	
===Tertiary Ratings===
Added in Patch 6.0.2, these bonus stats have a chance to appear on gear from certain sources. Some items and player abilities (e.g. Soul Rending) grant these stats as well.
Rating 	Effect 	Level 10	Level 25	Level 50	Level 60	Level 70
Avoidance	-1% Damage from Area of Effect attacks 	1.08 	1.84 	4.27 	14 	72
Leech 	1% of Damage and Healing returned as Healing	1.62 	2.76 	6.4 	21 	110
Speed 	1% Increased Movement Speed 	0.77 	1.31 	3.05 	10 	50
===Defensive ratings===
These ratings were commonly referred to as avoidance ratings (prior to the introduction of the Avoidance stat), and are not currently itemized on end-game gear and can usually only be found on some leveling or older raiding gear, or from bonuses like Azerite Traits. For some classes and specs, these are gained passively through other stats (while protection warriors gain parry chance from strength, they also receive parry rating from critical strike rating via Riposte). 
Rating	Effect 	Level 10	Level 25	Level 50	Level 60	Level 70
Dodge 	1% dodge chance	3.01 	5.12 	11.89 	39 	200
Parry 	1% parry chance	3.01 	5.12 	11.89 	39 	200
* Dodge and parry ratings also feature diminishing returns, though the way they diminish is different from combat ratings.
* Classes who cannot parry attacks gain no effect from parry rating.
==Diminishing returns==
Beginning with patch 9.0.1, combat stat ratings start to have diminishing returns above 30% stat gained from rating. This effect causes a ramping "penalty" on further stat rating gains, requiring more rating to receive an additional 1%. The amount diminished is based upon fixed stat brackets (or soft caps). 
This penalty does not count secondary stat gains from fixed stat percentage buffs (such as Heroism).
Stat from Rating	Rating Penalty
0 - 30% 	No effect
30 - 39% 	10% penalty
39 - 47% 	20% penalty
47 - 54% 	30% penalty
54 - 66% 	40% penalty
66 - 126% 	50% penalty
126% 	No stat gain
* The penalty only applies to rating gained above its minimum bracket.
* All secondary stats have a maximum value (or hard cap) of 126%, meaning that additional stat rating has no effect.
* This system does not apply to dodge or parry ratings, which have their own diminishing return formula.
==Removed secondary stats==
The following combat ratings are either no longer itemized on gear or have been removed from game. This chart is purely for historical purposes, and will not be updated to reflect future events (such as a stat squish).
Rating 	Effect 	Level 60	Level 70	Level 80	Level 85	Level 90	Level 90 Squished	Level 100	Patch Removed	
Armor Penetration 	1% Armor Ignored 	3.75 	5.92 	12.31 	- 	- 	- 	- 	Patch 4.0.1 	
Defense Rating 	+1 Defense Skill 	1.5 	2.37 	4.92 	- 	- 	- 	- 	Patch 4.0.1 	
Block Rating 	1% block chance 	6.9 	10.8808 	22.6251 	88.3594 	295.0 	- 	- 	Patch 4.0.1 	
Physical hit 	1% hit chance 	9.37931 	14.7905 	40.7548 	102.446 	340.0 	- 	- 	Patch 6.0.2 	
Spell hit 	1% spell hit chance 	8 	12.6154 	26.232 	102.446 	340.0 	- 	- 	Patch 6.0.2 	
Expertise 	-1% Dodge/Parry and 1% Spell Hit 	2.34483 	3.69761 	7.68869 	102.446 	340.0 	- 	- 	Patch 6.0.2 	
PvP Resilience 	-1% Damage from Players 	9.292 	14.652 	30.467 	92.316 	310.0 	12.0 	56.0 	Patch 6.0.2 	
PvP Power 	1% Damage/Healing to Players 	7.964 	12.559 	26.115 	79.128 	265.0 	10.0 	49.0 	Patch 6.0.2 	
Multistrike 	2 chances to do an extra 30% damage 	N/A 	N/A 	N/A 	N/A 	N/A 	14.0 	66.0 	Patch 7.0.3 	
Weapon Skill Rating	+1 Weapon Skill (to specific weapon type)	2.5 	3.9 	- 	- 	- 	- 	- 	Patch 2.3.0 	
Notes:
Physical hit chance and spell hit chance were distinct attributes derived from the same hit rating (now retired).
Physical critical strike chance and spell critical strike chance were distinct attributes derived from the same critical strike rating (now equal).
Haste effects attack speed, casting speed and non-mana resource (e.g. energy, runes) regeneration.
==Wrath of the Lich King: Classic==
The following tables display the secondary stat ratings present in Wrath of the Lich King Classic and the necessary amounts of rating needed per 1% secondary stat (or 1 point for Expertise, 1 skill point for Defense). 
Secondary stats that are not itemized as ratings (Spell Penetration, MP5, etc.) are not included as these stats do not use the combat rating system and thus have the same effect at all levels.
 Offensive Ratings
Rating 	Effect 	Level 60	Level 70 	Level 80
Armor Penetration	1% armor ignored 	3.75 	5.92 	12.31
Expertise 	1 point of expertise(-0.25% dodge/parry chance)	2.5 	3.94 	8.2
Hit 	1% hit chance1% spell hit chance 	108 	15.7612.62	32.7926.23
Critical Strike 	1% critical strike chance 	14 	22.08 	45.91
Haste 	1% haste 	10 	15.76 	32.79
 Defensive Ratings
Rating 	Effect 	Level 60	Level 70	Level 80
Defense 	1 defense skill*	1.5 	2.37 	4.92
Dodge 	1% dodge* 	13.8 	21.76 	45.25
Parry 	1% parry* 	13.8 	21.76 	45.25
Block 	1% block chance 	5 	7.88 	16.4
Resilience	1% resilience 	28.75 	45.34 	94.27
*Before diminishing returns.
====Additional Notes====
*Expertise is converted from rating to points, rather than a direct percentage. 
**1 Expertise point reduces a target's chance to dodge and parry attacks by 0.25%. Therefore, it takes 4 points of Expertise to reduce a target's dodge/parry chance by 1%.
**Expertise rating is rounded down to the nearest full point (e.g. rating equal to 4.85 Expertise points will give only 4 Expertise points). This means that expertise rating cannot give partial amounts of expertise points, and additional rating has no effect until the next full point is reached.
*Defense skill: Diminishing returns on Defense rating only apply to the dodge, parry, and miss chances provided by defense skill. The chances to block and receive a critical strike are not affected by diminishing returns.
*Haste: Death Knights, Druids, Shaman, and Paladins receive 30% more melee haste from haste rating than other classes. This reduces the amount of haste rating these classes need per 1% melee haste (these values are not displayed in the above chart).
*Resilience provides multiple effects with differing amounts per "1%" Resilience.
** 1% Resilience reduces the chance to receive a critical strike by 1%, reduces critical strike damage received by 2.2%, reduces the effect of mana drains by 2.2%, and reduces damage taken from players and their pets by 2%.
** Resilience cannot reduce the damage done by critical strikes by more than 33%, but its other effects are not capped.
====Changes from Burning Crusade: Classic====
*Armor Penetration is now a stat rating. Previously, it reduced armor by a flat amount like spell penetration does to resistances.
*Hit, Crit, and Haste ratings now affect spells, and there are no longer separate spell ratings on gear.
**Spell hit chance continues to require less rating per 1% than melee/ranged hit chance.
*Defense, Dodge, and Parry ratings are now affected by diminishing returns. Parry diminishes faster than Dodge.
*Dodge, Parry, and Resilience now require different rating amounts to reach 1% at all levels than they did in Patch 2.5.4. Parry requires less rating, the others require more.
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==See also==
*Item level
*Attack table
==References==
Category:Formulas and game mechanics
Category:Tanking