Blocking
Blocking is a means of preventing damage from enemy attacks by fending with a shield, staff or dual wielded weapons.
The base chance to block when using a shield (24-32%) or a staff (12-18%) is determined by the base item type. When dual wielding, the base chance to block is 15% no matter which weapons are used.
Additional chance to block can be gained by taking certain passive skills, using 
Tempest Shield, equipping a shield with the modifier Local Additional Block Chance %, or equipping unique items such as 
The Bringer of RainThe Bringer of Rain
Nightmare BascinetArmour: (486-748)
Evasion: (699-1072)Requires Level 67, 62 Str, 85 DexSocketed Gems are Supported by Level 30 Melee Physical Damage
Socketed Gems are Supported by Level 30 Faster Attacks
Socketed Gems are supported by Level 30 Blind
6% Chance to Block Attack Damage
Adds 20 to 30 Physical Damage to Attacks
(200-300)% increased Armour and Evasion
+(200-300) to maximum Life
20% chance to gain an Endurance Charge when you Block
Can't use Chest armour
Extra gore"What lies beneath your feet?!"
"Sacred ground, watered with tears of blood!"
.
Usually only attacks can be blocked, but there are passives and unique items that apply a percentage of block chance to spells. For example, the unique amulet 
Stone of LazhwarStone of Lazhwar
Lapis AmuletRequires Level 5+(20-30) to Intelligence(12-15)% Chance to Block Spell Damage
(15-20)% increased Cast Speed
+(40-70) to maximum ManaYou are slow, foolish and ignorant.
I am not.
grants 50% of Block Chance applied to Spells. A character with 40% block chance would have 40% (attack) block chance and 20% spell block chance with the unique equipped.
Block chance is capped at 75%. The chance to block spells is also capped at 75%. The only exception comes from the unique 
The AnvilThe Anvil
Amber AmuletRequires Level 45+(20-30) to Strength(10-15)% Chance to Block Attack Damage
10% reduced Attack Speed
10% reduced Cast Speed
+(400-500) to Armour
(34-48) Life gained when you Block
(18-24) Mana gained when you Block
+3% to maximum Chance to Block Attack Damage
Reflects 240 to 300 Physical Damage to Attackers on BlockForge your Perseverance on the Anvil of Faith.
which raises the cap to 78%.
Mechanics
Blocking an attack prevents all damage and harmful effects including status ailments. Reflected damage can be blocked.[1]
When an attack is blocked, the game also calculates if the attack would have caused a stun were it not blocked. If it would have caused a stun, the blocking animation is played, stunning you briefly. If it would not have caused a stun, then you get a "free" block with no animation. Faster Block and Stun Recovery and Increased Block Recovery modifiers reduce the length of the blocking animation.
The following formula is the complete calculation for the duration of the blocking animation (in milliseconds). If you cannot be stunned, the block animation will never play.
Block Duration = 350 / ( 1 + Block and Stun Recovery + Block Recovery )
Status ailments have no affect on your block chance, but being frozen will prevent the block animation from playing if it otherwise would, and chilled will make it take longer to play (since those two work by decreasing the speed at which your character plays animations).
On hit effects from skills like Module Error: Too many skills found with q_where = skill.active_skill_name="Glacial Hammer". Please choose only one of the following ids:
CityStalkerGlacialHammer - 10% chance to Freeze enemies, 50% of Physical Damage Converted to Cold Damage (page)
GlacialHammerRoyale - 10% chance to Freeze enemies, 60% of Physical Damage Converted to Cold Damage, Every third successive strike Freezes enemies as though dealing (100-190)% more Damage, +(0.2-0.3) metres to Melee Strike Range, 35% increased Duration of Cold Ailments, (10-19)% increased Effect of Cold Ailments, Adds (3-20) to (4-30) Cold Damage against Chilled Enemies (page) and 
Viper Strike will still apply because block doesn't prevent a successful hit. However, skill effects based on damage like Module Error: Too many skills found with q_where = skill.active_skill_name="Puncture". Please choose only one of the following ids:
MonsterPuncture - +(112-197)% more Damage with Bleeding, Causes Bleeding (page)
MonsterPunctureAtAnimationSpeedUnique - +(112-197)% more Damage with Bleeding, Causes Bleeding (page) are essentially blocked.[2]
Related Unique Items
A number of unique items give bonuses to block, either by directly granting additional block chance, or indirectly by enhancing it in various ways. Note: Only unique items with explicit block-related mods are listed here. Ofcourse, all shields and staffs have implicit chance to block and they also apply on uniques, but they are not shown here.
Additional Block Chance
Aegis AuroraAegis Aurora
Champion Kite ShieldChance to Block: 32%
Armour: (860-1235)
Energy Shield: (176-250)
Movement Speed: -3%Requires Level 62, 85 Str, 85 Int(300-400)% increased Armour and Energy Shield
+10% to all Elemental Resistances
+5% to maximum Cold Resistance
+6% Chance to Block
Recover Energy Shield equal to 2% of Armour when you Block
(10-20)% increased Elemental Damage with Attack SkillsBorn from the marriage of ice and sky,
the aurora evokes both awe and power.
Crest of PerandusCrest of Perandus
Pine BucklerChance to Block: 31%
Evasion: (51-66)
Movement Speed: -3%Requires Level 8, 26 Dex3% increased Movement Speed+(60-80) to maximum Life
Regenerate (5-7.5) Life per second
+30% to Lightning Resistance
0.6% of Physical Attack Damage Leeched as Life
+5% Chance to Block"With piety and justice."
- Perandus family motto
KaltenhaltKaltenhalt
Painted BucklerChance to Block: 29%
Evasion: (196-308)
Movement Speed: -3%Requires Level 16, 44 Dex6% increased Movement Speed(60-100)% increased Evasion Rating
+5% to maximum Cold Resistance
+50% to Cold Resistance
Gain (10-15)% of Physical Damage as Extra Cold Damage
Reflects (25-50) Cold Damage to Melee Attackers
+5% Chance to BlockCold, miserable and alone... but alive.
Lioneye's RemorseLioneye's Remorse
Pinnacle Tower ShieldChance to Block: 30%
Armour: (1307-1718)
Movement Speed: -3%Requires Level 70, 159 Str+(20-30) to maximum Life(180-220)% increased Armour
20% increased Stun and Block Recovery
+(160-180) to maximum Life
5% reduced Movement Speed
-25 Physical Damage taken from Projectile Attacks
+5% Chance to BlockMarceus' unblemished shield is a testament
to his arrogance... and his fate.
- The Bringer of RainThe Bringer of Rain
Nightmare BascinetArmour: (486-748)
Evasion: (699-1072)Requires Level 67, 62 Str, 85 DexSocketed Gems are Supported by Level 30 Melee Physical Damage
Socketed Gems are Supported by Level 30 Faster Attacks
Socketed Gems are supported by Level 30 Blind
6% Chance to Block Attack Damage
Adds 20 to 30 Physical Damage to Attacks
(200-300)% increased Armour and Evasion
+(200-300) to maximum Life
20% chance to gain an Endurance Charge when you Block
Can't use Chest armour
Extra gore"What lies beneath your feet?!"
"Sacred ground, watered with tears of blood!" - The AnvilThe Anvil
Amber AmuletRequires Level 45+(20-30) to Strength(10-15)% Chance to Block Attack Damage
10% reduced Attack Speed
10% reduced Cast Speed
+(400-500) to Armour
(34-48) Life gained when you Block
(18-24) Mana gained when you Block
+3% to maximum Chance to Block Attack Damage
Reflects 240 to 300 Physical Damage to Attackers on BlockForge your Perseverance on the Anvil of Faith. (also increases maximum block chance) 
Thousand Teeth TemuThousand Teeth Temu
Vaal BucklerChance to Block: 37%
Evasion: (660-833)
Movement Speed: -3%Requires Level 63, 159 Dex3% increased Movement Speed(100-120)% increased Evasion Rating
+(70-90) to maximum Life
0.4% of Physical Attack Damage Leeched as Life
+10% Chance to Block
Reflects 1000 to 10000 Physical Damage to Attackers on BlockCrimson burn'd the star of sadness,
All was woe that seem'd but gladness.
Additional Block Chance while Dual Wielding
Prismatic EclipsePrismatic Eclipse
Twilight BladeOne Handed Sword
Physical Damage: (90-100) to (157-166)
Critical Strike Chance: 5.00%
Attacks per Second: 1.30
Weapon Range: 1.1 metresRequires Level 53, 91 Str, 91 Dex40% increased Global Accuracy Rating+8% Chance to Block Attack Damage while Dual Wielding
Adds (60-70) to (71-80) Physical Damage
25% increased Global Physical Damage with Weapons per Red Socket
12% increased Global Attack Speed per Green Socket
0.4% of Physical Attack Damage Leeched as Mana per Blue Socket
+0.2 metres to Melee Strike Range per White Socket"A raging Solaris seared and contorted the orb's surface.
A despairing Lunaris filled the scars with her tears.
Yet Viridi remained, trapped within, forever more."
- Azmerian Creation Myth
Ungil's GaucheUngil's Gauche
Boot KnifeRune Dagger
Physical Damage: (14.4-16) to (61.2-68)
Elemental Damage: 3-30
Critical Strike Chance: 6.30%
Attacks per Second: 1.59
Weapon Range: 1.0 metresRequires Level 20, 31 Dex, 45 Int30% increased Global Critical Strike Chance+12% Chance to Block Attack Damage while Dual Wielding
+(10-20) to Dexterity
(80-100)% increased Physical Damage
Adds 3 to 30 Lightning Damage
10% increased Attack Speed
50% increased Global Critical Strike ChanceUnwieldy and garish became graceful
and deadly in Ungil's nimble hands.
Essentia SanguisEssentia Sanguis
Vaal ClawClaw
Physical Damage: 29-76
Elemental Damage: 1 to (600-700)
Critical Strike Chance: 6.50%
Attacks per Second: (1.56-1.69)
Weapon Range: 1.1 metresRequires Level 66, 95 Dex, 131 Int2% of Physical Attack Damage Leeched as Life+8% Chance to Block Attack Damage while Dual Wielding Claws
Adds 1 to (600-700) Lightning Damage
(20-30)% increased Attack Speed
+(30-40) to maximum Energy Shield
Energy Shield Leech Effects from Attacks are not removed at Full Energy Shield
Ghost ReaverThe darkest clouds clashed and coupled,
giving birth to four lightning children of hate.
Wings of EntropyWings of Entropy
Ezomyte AxeTwo Handed Axe
Physical Damage: (139.2-156.6) to (209.6-235.8)
Critical Strike Chance: 5.70%
Attacks per Second: 1.35
Weapon Range: 1.3 metresRequires Level 62, 140 Str, 86 Dex(7-10)% Chance to Block Spell Damage
+(8-12)% Chance to Block Attack Damage while Dual Wielding
(60-80)% increased Physical Damage
Adds (75-100) to (165-200) Fire Damage in Main Hand
Adds (75-100) to (165-200) Chaos Damage in Off Hand
Counts as Dual WieldingFire and Anarchy are the most reliable agents of change.
% Applied to Spell Block
- Stone of LazhwarStone of Lazhwar
Lapis AmuletRequires Level 5+(20-30) to Intelligence(12-15)% Chance to Block Spell Damage
(15-20)% increased Cast Speed
+(40-70) to maximum ManaYou are slow, foolish and ignorant.
I am not. 
RainbowstrideRainbowstride
Conjurer BootsEnergy Shield: (36-42)Requires Level 53, 94 Int(15-20)% Chance to Block Spell Damage
+(40-60) to maximum Mana
+20% to all Elemental Resistances
20% increased Movement Speed"They say that you should take life's troubles in your stride.
Some men have a longer stride than others."
- Gaius Sentari
Rathpith GlobeRathpith Globe
Titanium Spirit ShieldChance to Block: 25%
Energy Shield: (147-200)
Movement Speed: -3%Requires Level 68, 159 Int(10-15)% Chance to Block Spell Damage
(120-160)% increased Energy Shield
10% increased maximum Life
Sacrifice 10% of your Life when you Use or Trigger a Spell Skill
5% increased Critical Strike Chance for Spells per 100 Player Maximum Life
5% increased Spell Damage per 100 Player Maximum LifeThe Vaal emptied their slaves of beating hearts,
and left a mountain of twitching dead.
Daresso's CourageDaresso's Courage
Baroque Round ShieldChance to Block: 25%
Armour: (366-490)
Evasion: (366-490)
Movement Speed: -3%Requires Level 54, 70 Str, 70 Dex120% increased Block Recovery+30% Chance to Block Spell Damage while on Low Life
(200-250)% increased Armour and Evasion
+(20-30)% to all Elemental Resistances
+100% Chance to Block Attack Damage if you have Blocked Spell Damage Recently
+100% chance to Block Spell Damage if you have Blocked Attack Damage RecentlyBy tourney's end, Daresso bled and shivered.
Yet even accursed treachery failed to steal the champion's victory.
Saffell's FrameSaffell's Frame
Branded Kite ShieldChance to Block: 24%
Armour: (186-208)
Energy Shield: (38-43)
Movement Speed: -3%Requires Level 59, 76 Str, 76 Int+4% to all Elemental Resistances(20-30)% Chance to Block Spell Damage
(20-30)% increased Spell Damage
+(20-30)% to all Elemental Resistances
+4% to all maximum Resistances
Cannot Block Attack DamageA swift mind solves problems before they occur.
- Wings of EntropyWings of Entropy
Ezomyte AxeTwo Handed Axe
Physical Damage: (139.2-156.6) to (209.6-235.8)
Critical Strike Chance: 5.70%
Attacks per Second: 1.35
Weapon Range: 1.3 metresRequires Level 62, 140 Str, 86 Dex(7-10)% Chance to Block Spell Damage
+(8-12)% Chance to Block Attack Damage while Dual Wielding
(60-80)% increased Physical Damage
Adds (75-100) to (165-200) Fire Damage in Main Hand
Adds (75-100) to (165-200) Chaos Damage in Off Hand
Counts as Dual WieldingFire and Anarchy are the most reliable agents of change.
miscellaneous
Cybil's PawCybil's Paw
Thresher ClawClaw
Physical Damage: 20-53
Critical Strike Chance: 6.50%
Attacks per Second: 1.30
Weapon Range: 1.1 metresRequires Level 37, 53 Dex, 77 IntGrants 25 Life per Enemy Hit(15-20)% increased Cast Speed
+(30-40) to maximum Mana
Gain (15-20) Life per Enemy Hit with Spells
8% increased Spell Damage per 5% Chance to Block Attack DamageTread lightly, lest their vigil find you.
Speak softly, lest their reason fend you.
Cut gently, lest their spirit haunt you.
- Module Error: No results found for item using search term "item_name = Titucus Span"
Lightbane RaimentLightbane Raiment
Ornate RingmailArmour: (569-715)
Energy Shield: (118-148)
Movement Speed: -5%Requires Level 47, 69 Str, 69 Int(120-140)% increased Armour and Energy Shield
30% of Physical Damage Converted to Chaos Damage
Reflects 30 Chaos Damage to Melee Attackers
25% reduced Light Radius
100% chance to create Desecrated Ground when you Block
Desecrated Ground deals 250 Chaos Damage per second (Hidden)
Desecrated Ground has a radius of 16 (Hidden). . . and the Light faded and hope waned
Zahndethus cast aside his faith
and embraced the darkness.
Zahndethus' CassockZahndethus' Cassock
Sage's RobeEnergy Shield: (177-225)
Movement Speed: -3%Requires Level 37, 104 IntAdds 1 to 40 Lightning Damage to Attacks
(125-150)% increased Energy Shield
+(40-50)% to Chaos Resistance
25% increased Light Radius
100% chance to create Consecrated Ground when you Block
Consecrated Ground regenerates 6% Life per second (Hidden)
Consecrated Ground has a radius of 18 (Hidden)When dead men rise and darkness falls
Only faith can be your walls
Walls of Light, not of brick
Twice as strong and twice as thick
Rumi's ConcoctionRumi's Concoction
Granite FlaskLasts 6.00 Seconds
Consumes 30 of 60 Charges on use
+1500 to ArmourRequires Level 68+(8-12)% Chance to Block Attack Damage during Effect
+(4-6)% Chance to Block Spell Damage during Effect"Yesterday I was clever, so I wanted to change the world.
Today I am wise, so I am changing myself."
-Rumi of the VaalRight click to drink. Can only hold charges while in belt. Refills as you kill monsters.
Passives
There are passive skill nodes that grant additional chance to block or a combination of bonuses including chance to block.
Chance to Block with Shield
Chance to Block with Staff
Chance to Block while Dual Wielding
Block Recovery
References
- ↑ Mark_GGG (December 3, 2012). "Mechanics Thread". Path of Exile Forum. Retrieved October 21, 2013.
- ↑ Mark_GGG (November 5, 2012). "Viper Strike overriding block chance/dodge/evasion". Path of Exile Forum. Retrieved October 21, 2013.