Block < onlyinclude > < / onlyinclude > Block is the ability of a shield to absorb melee damage in addition to its armor value . When a shield is equipped , you have a certain chance to perform a block , the amount of damage of which is influenced by block value . The basic chance to block an attack is indicated on your character sheet under the Defense tab . This value assumes that you fight against a mob or other character of same level . Fighting a mob of higher level than yourself decreases your chance to block , and vice versa . Usability . The fact that a Block may only mitigate damage partly — which means the enemy ' s attack speed and damage per attack becomes a factor — and the fact that the talents increasing Block chance cannot reliably be active at all times , makes it harder to calculate the actual benefit of Block in comparison to other damage mitigation mechanics , such as armor or chance to get missed . Mob rules . While it is clear that a Blocked attack made against a " player " cannot be a crit , it is possible that mobs have different rules for determining whether an incoming attack is blocked or not , which includes the possibility of a " blocked crit " . It should be noted , however , that only special attacks — i . e . yellow - damage instant attacks such as Claw , Overpower , and Sinister Strike , and yellow - damage on - next - swing attacks such as Heroic Strike and Raptor Strike — have been observed as inflicting blocked crits . Normal white - damage auto - attacks have never been seen inflicting a blocked crit , and are probably subject to the same mutually - exclusive - attack - result rules that attacks made against players are . Note too , that unlike player characters , mobs sometimes block attacks even though they have no shield equipped . Chance to block . Your base chance to block an attack is 5 % and this is modified by a factor of the rating difference between the attacker ' s weapon skill and the defender ' s defense and block rating . Each point of difference adjusts the base chance by 0 . 1 % if the target is a mob and 0 . 04 % if the target is a player . Mobs level 9 and lower do not block as frequently , just as they are not miss ed as frequently as they should be . Also , mobs cannot block more than 5 % of attacks regardless of rating difference . The formula : Block % = 5 % base chance + contribution from Block Rating + contribution from talents + ( ( Defense skill - attacker ' s weapon skill ) * 0 . 04 ) In combat , you will notice that the percentage of incoming attacks that are Blocked matches the Block percentage shown in your tooltips . Miss chance and Critical chance are unmodified by your Block chance , so you ' re not " wasting " Blocks on misses nor are you able to Block a Critical . This may seem odd to some folks if they are expecting a " if hit , then check if Parry , then check if Block , then check . . . " type system . WoW , like many other games , uses a combat results table - based combat scheme ( where one roll determines outcome of an attack ) , so percentages are absolute . Your parsed Block percentage won ' t necessarily match your tooltip if you ' re fighting creatures higher or lower in level to you . See the Defense formula above to understand . Damage reduction . The amount of damage a Block reduces depends on the block value of your shield , any enchantments , talents and your Strength . Damage reduced by blocking is calculated after other damage reducing factors , such as armor , which increases the effectiveness of blocking . Block value modifiers . Block value modifiers that increase block value by a percentage are added together as modifiers before being applied to the character ' s base block value . For example , a Warrior ' s Shield Block skill increases block chance and value by 100 % , and most tanking Warriors will also have the Shield Mastery talent ( + 30 % block value ) . This is calculated in the following fashion : The modifier is 2 . 3 ( 230 % ) because the bonuses from Shield Block ( 100 % ) have been added to Shield Mastery ( 30 % ) before being applied to the base block value ( 100 % ) . Temporary block value from librams , trinkets , or other items is included in the original base block value calculation , and therefore benefits from all block value modifiers . The quantity of damage blocked is calculated " after " damage mitigation from all other sources ( Armor , Defensive Stance , Improved Righteous Fury , Blessing of Sanctuary , etc . ) . That means if the opponent hits you for 200 , mitigated to 100 by Armor , and block according to the formula above is 40 , then you will see in your combat window : " . . . hits you for 60 . ( 40 blocked ) " . If the block quantity is greater than the damage received after mitigation , you will then block 100 % of the damage : " . . . attacks . You block . " Changes for Cataclysm . As of Cataclysm the mechanics behind block will be changed dramatically . Instead of blocking a flat amount of damage you will then always block 30 % of the damage , with block rating still defining how often you will block . This means that the Block Value stat will be gone , though the 30 % will likely become subject of talents and / or glyphs , one known block modifier in Cataclysm will be the Protection Warrior ' s Mastery bonus : Critical Block which has a chance to block twice as much incoming damage .