Chance to Block Mechanics

Chance to Block is a mechanic that has defensive and offensive implications. Negating all damage of an attack that has been blocked, it is a significant boost for your survivability when used as an additional layer of defense. To use it as such, you have to sacrifice maximum Life. However, it becomes incredibly important for Characters engaged in front line fights, and for Hardcore in general.

Monsters also benefit from Chance to Block.

Mechanics

• While wearing a Shield, a Character has a % Chance to Block. This can be seen by hovering over the Defense value on your Character Screen. Chance to Block is capped at 75% while using Skills without movement, standing, walking or using Whirlwind.
• When running, the % Chance to Block is reduced to 1/3, reducing the cap to 25%.
• A successful block negates the damage from the incoming attack.
• The total % Chance to Block is determined using the Character Level (clvl), a Character specific bonus, the base % Chance to Block on the Shield, sources of "x% Increased Chance of Blocking", and the total Dexterity value.
• The % Chance to Block is applied after an attack successfully passes the hit check but before the Amazon's Dodge, Avoid, and Evade.
• Successful blocks trigger an animation. The duration of this animation is determined by the Block Rate Breakpoint, which is influenced by the Affix "+x% Faster Block Rate".
• You can block immediately after the animation of a previous block is over. This can cause you to get into a "Block-Lock".

What can be blocked?

While most attacks can be blocked, there are a number of exceptions. There are also some unintuitive sources of incoming damage that can be blocked. Check out the following table:

Calculations

Dexterity required for 75% Chance to Block

The most frequent question in regard to Chance to Block is: "How much Dexterity do I need to reach 75%"? To calculate this, we need the following 3 variables:

• Shield = Base Chance to Block of the used Shield, including the Character's bonus
• Bonus = Sum of all "x% Increased Chance of Blocking" values and Holy Shield when active
• clvl = Character Level

Formula

Dexterity = 15 + ceil(150 * clvl / (Shield + Bonus))

Example:

Current % Chance to Block

To calculate the current % Chance to Block, we need the following 4 variables:

• Shield = Base Chance to Block of the used Shield, including the Character bonus
• Bonus = Sum of all "x% Increased Chance of Blocking" values and Holy Shield when active
• Dexterity = Total value of Dexterity (Character Screen)
• clvl = Character Level

Formula

CTB = min(floor((Shield + Bonus) * (Dexterity - 15) / (clvl * 2)), 75) %

Example

Base Chance to Block

Every Shield in Diablo 2 has a base % Chance to Block, shown in the tooltip. This % is the sum of the Shield's base value and a bonus value, which depends on the Character that looks at the Shield.

Character Bonuses

Shield Values

Adding these values to the Shield bases lead to the following % Chance to Block values displayed in the game, including the Character bonus. If you hover over the Shield name on the left, you can see the base value without the Character bonus, in the following accordions:

Normal Shields

Shield Base	Amazon Assassin Barbarian	Druid Necromancer Sorceress	Paladin
Buckler	25%	20%	30%
Small Shield	30%	25%	35%
Large Shield	37%	32%	42%
Spiked Shield	35%	30%	40%
Kite Shield	33%	28%	38%
Bone Shield	45%	40%	50%
Tower Shield	49%	44%	54%
Gothic Shield	41%	36%	46%

Exceptional Shields

Shield Base	Amazon Assassin Barbarian	Druid Necromancer Sorceress	Paladin
Defender	35%	30%	40%
Round Shield	37%	32%	42%
Scutum	39%	34%	44%
Barbed Shield	42%	37%	47%
Dragon Shield	43%	38%	48%
Grim Shield	45%	40%	50%
Pavise	49%	44%	54%
Ancient Shield	41%	36%	46%

Elite Shields

Shield Base	Amazon Assassin Barbarian	Druid Necromancer Sorceress	Paladin
Heater	47%	42%	52%
Luna	45%	40%	50%
Hyperion	49%	44%	54%
Blade Barrier	45%	40%	50%
Monarch	47%	42%	52%
Troll Nest	45%	40%	50%
Aegis	49%	44%	54%
Ward	49%	44%	54%

Auric Shields (Only Paladin)

Only a Paladin can equip Auric Shields, however, when other Characters look at an Auric Shield, their tooltip shows the % Chance to Block using their Character's bonus.

Normal

Shield Base	Chance to Block
Targe	40%
Rondache	45%
Heraldic Shield	50%
Aerin Shield	52%
Crown Shield	55%

Exceptional

Shield Base	Chance to Block
Akaran Targe	40%
Akaran Rondache	45%
Protector Shield	50%
Gilded Shield	52%
Royal Shield	55%

Elite

Shield Base	Chance to Block
Sacred Targe	60%
Sacred Rondache	58%
Kurast Shield	55%
Zakarum Shield	52%
Vortex Shield	49%

Voodoo Heads (Only Necromancer)

Only a Necromancer can equip Voodoo Shields, however, when other Characters look at a Voodoo Shield, their tooltip shows the % Chance to Block using the Character's bonus.

Normal

Shield Base	Chance to Block
Preserved Head	23%
Zombie Head	25%
Unravaler Head	28%
Gargoyle Head	30%
Demon Head	32%

Exceptional

Shield Base	Chance to Block
Mummified Trophy	23%
Fetish Trophy	25%
Sexton Trophy	28%
Cantor Trophy	30%
Hierophant Trophy	32%

Elite

Shield Base	Chance to Block
Minion Skull	23%
Hellspawn Skull	25%
Overseer Skull	28%
Succubus Skull	30%
Bloodlord Skull	32%

Increased Chance of Blocking

In the calculation for the total % Chance to Block, the summed up % value of this Affix, across all item slots, is added to the base % Chance to Block of the Shield. If this Affix is on the Shield, it shows in the tooltip of the Shield. It doesn't add to the tooltip, if it comes from other item slots.

Sources

Shields

1)The tooltip, when hovered over, shows the % Chance to Block, using a Barbarian.

Regular Shields

Shields		Increased Chance of Blocking
Magic Shield of Blocking1 Rare Shield1		10%
Magic Shield of Deflecting1 Rare Shield1		20%
Caster Crafted Shield		5-10%
Hit Power Crafted Shield		5-10%
Rhyme		20%
Sanctuary		20%
Sigon's Guard		20%
Civerb's Ward		15%
Whitstan's Guard		55%
Taebaek's Glory		25%
Pelta Lunata		20%
Umbral Disk		30%
Stormguild		30%
Swordback Hold		20%
Steelclash		25%
Bverrit Keep		10%
The Ward		10%
Visceratuant		30%
Moser's Blessed Circle		25%
Stormchaser		20%
Gerke's Sanctuary		30%
Radament's Sphere		20%
Spirit Ward		20-30%
Stormshield		25%

Auric Shields

Auric Shields		Increased Chance of Blocking
Herald of Zakarum		30%
Griswold's Honor		20%
Alma Negra		20%

Voodoo Heads

Voodoo Heads:		Increased Chance of Blocking
Homunculus		40%
Trang-Oul's Wing		30%

Other Sources

Source		Increased Chance of Blocking
Eld Rune socketed in a Shield		7%
Safety Crafted Amulets		1-10%
Full Isenhart's Armory Set bonus		30%
Twitchthroe		25%
Guardian Angel		20%
Swordguard		20%

Block Rate

Blocking is an animation that is performed when you successfully block a physical attack. This includes the Assassins' Weapon Block. Your Block Rate determines how fast this animation is performed.

Mechanics

• While blocking, you are unable to perform any actions.
• You can block consecutive attacks, as soon as your animation finishes, potentially leading to a full "block lock".
• You can speed up the animation by using gear with +xx% Faster Block Rate (FBR).
  • This Affix is exclusive to Shields, making it very hard to come by. The only exceptions to this rule are Guardian Angel and Pattern.

Calculations

Note for the calculations:

• ceil = round up the term that follows
• floor = round down the term that follows

Before we can use the formulas for Block Rate, we need the following values:

• The total +xx% Faster Block Rate from our gear.
• The "Block Base" of the Character. Check in the table below.
• The "Animation Speed" of the Character. Check in the table below.

With these values, we can go through the following formulas.

Effective Faster Block Rate (EFBR):

EFBR = floor(FBR * 120 / (FBR + 120))

With Holy Shield

EFBR = floor(FBR * 120 / (FBR + 120)) + 50

Block Frames

Block Frames = ceil(256 * Block Base / floor(Animation Speed * (50 + EFBR) / 100) - 1)

Character	Block Base	Animation Speed
Amazon	3	256
Amazon (1-handed Weapons) (*)	3	88
Assassin	3	256
Barbarian	4	256
Druid	6	256
Werewolf	5	256
Werebear	5	200
Necromancer	6	256
Paladin	3	256
Sorceress	5	256

(*) This only means: 1-handed Axes, Clubs, Maces, Hammers, Scepters, Swords, Throwing Axes.

Practical Example

Practical example with 50 FBR on a Paladin without Holy Shield:

Effective Faster Block Rate (EFBR)

EFBR = floor(6,000 / 170)
EFBR = floor(35.294...)
EFBR = 35

Block Frames

Block Frames = ceil(768 / floor(256 * 85 / 100) -1)
Block Frames = ceil(768 / 217 - 1)
Block Frames = ceil(2.539...)
Block Frames = 3

This means the Paladin with 50 FBR and without Holy Shield uses 3 Frames for the Block animation.

Practical example with 50 FHR on a Paladin with Holy Shield:

Effective Faster Block Rate (EFBR)

EFBR = floor(6,000 / 170) + 50
EFBR = floor(35.294...) + 50
EFBR = 85

Block Frames

Block Frames = ceil(768 / 345 - 1)
Block Frames = ceil(1.226...)
Block Frames = 2

This means the Paladin with 50 FBR and with Holy Shield uses 2 Frames for the Block animation.

Breakpoints

+140% Faster Block Rate (155% on Paladin) is the maximum you can achieve. The tables below show the Breakpoints with achievable Faster Block Rate values.

Amazon

1-Handed Swinging Weapons (Axes, Clubs, Maces, Scepters, Swords, Throwing Axes, and Wands):

Faster Block Rate	0	4	6	11	15	23	29	40	56	80	120
Block Frames	17	16	15	14	13	12	11	10	9	8	7

Other Weapons:

Faster Block Rate	0	13	32	86
Block Frames	5	4	3	2

Assassin

Faster Block Rate	0	13	32	86
Block Frames	5	4	3	2

Barbarian

Faster Block Rate	0	9	20	42	86
Block Frames	7	6	5	4	3

Druid

Human form:

Faster Block Rate	0	6	13	20	32	52	86
Block Frames	11	10	9	8	7	6	5

Werewolf:

Faster Block Rate	0	7	15	27	48	86
Block Frames	9	8	7	6	5	4

Werebear:

Faster Block Rate	0	5	10	16	27	40	65	109
Block Frames	12	11	10	9	8	7	6	5

Necromancer

Faster Block Rate	0	6	13	20	32	52	86
Block Frames	11	10	9	8	7	6	5

Paladin

Without Holy Shield:

Faster Block Rate	0	13	32	86
Block Frames	5	4	3	2

With Holy Shield:

Faster Block Rate	0	86
Block Frames	2	1

Sorceress

Faster Block Rate	0	7	15	27	48	86
Block Frames	9	8	7	6	5	4

Mercenaries and Pets

• No Mercenary can block attacks. The % Chance to Block from a Shield equipped on the Iron Wolf (Act 3 Mercenary) does not apply.
• Among all the Pet type minions, only the Necroskeleton (Raise Skeleton) has a 3% Chance to Block when using a Shield.
  Note: The visual model wearing a Shield is actually not an indicator whether it has a Chance to Block.
• The % Chance to Block from a Shield used to summon an Iron Golem is not applied to the Golem.

Monsters with Chance to Block

Hidden in the game files, monsters receive a % Chance to Block for each difficulty. They only execute that Chance to Block if they either spawn with a Shield and have a blocking animation enabled, or if they are tagged with "NoShldBlock" in the monstats.txt. Check out the tables below, showing what monsters have a Chance to Block with or without Shields.

Spawned WITH a Shield

• Monsters with no value in the Normal column don't spawn in normal. They are guest monsters throughout Act 5 in Nightmare and Hell difficulty.
• Monsters with no value in Normal and Nightmare don't spawn in these difficulties. They are guest monsters in the Pandemonium Event (see Ubers article) in Hell.

Monster	Normal	Nightmare	Hell
Dark Hunter	12%	12%	12%
Vile Hunter	18%	18%	18%
Dark Stalker	25%	25%	25%
Black Rogue	33%	33%	33%
Flesh Hunter	40%	40%	40%
Flesh Hunter	-	-	40%
Fallen	9%	9%	9%
Carver	16%	16%	16%
Devilkin	25%	25%	25%
Dark One	36%	36%	36%
Warped One	49%	49%	49%
Carver	-	49%	49%
Devilkin	-	49%	49%
Dark One	-	49%	49%
Huntress	15%	15%	15%
Sabre Cat	20%	20%	20%
Night Tiger	25%	25%	25%
Hell Cat	30%	30%	30%
Sabre Cat	-	15%	15%
Skeleton	10%	10%	10%
Returned	15%	15%	15%
Bone Warrior	20%	20%	20%
Burning Dead	25%	25%	25%
Horror	30%	30%	30%
Bone Warrior	-	30%	30%
Returned	-	30%	30%
Returned	-	-	30%
Slinger	15%	15%	15%
Spear Cat	16%	16%	16%
Hell Slinger	19%	19%	19%
Spear Cat	16%	16%	16%
Night Slinger	17%	17%	17%
Slinger	-	19%	19%
Slinger	-	19%	19%
Slinger	-	19%	19%

Block without Shield

Monster	Normal	Nightmare	Hell
Doom Knight1	24%	24%	24%
Hollow One2	0%	15%	33%
Guardian2	0%	15%	33%
Unraveler2	0%	15%	33%
Horadrim Ancient2	0%	15%	33%
Unraveler2	0%	15%	33%
Andariel	0%	20%	40%
Duriel	0%	25%	50%
Mephisto	20%	40%	50%
Diablo	25%	40%	50%
Baal	40%	45%	55%
Baal (clone)	40%	45%	55%
Diablo clone	-	-	50%
Lilith	-	-	40%
Uber Duriel	-	-	50%
Uber Mephisto	-	-	50%
Uber Diablo	-	-	50%
Uber Baal	-	-	55%

1. Applies to Doom Knights in Act 4 only. Doom Knights in Act 5 cannot block.
2. Applies to those spawning in Act 2 and Act 3, as well as Achmel the Cursed and his Minions in Act 5. Other monsters of this type spawned in Act 5 cannot block.

Summary

• Chance to Block is a very good way to mitigate damage taken from attacks.
• Chance to Block is more dangerous in the early game, than the benefits of Blocking because you have to sacrifice Vitality. Once you have a good Shield, consider speccing into Chance to Block.
• Hardcore players should consider going for 75% (max) Chance to Block with almost every build.
• The Block Animation speed is improved by +x% Faster Block Rate.
• You can get "Block-Locked", meaning you block multiple times in a row and you are not able to take any other actions.
• Some monsters have a Chance to Block, even if they don’t show the animation.

Phew... This post was longer than expected. As this is a very important mechanic, it is well worth the read. Make yourself familiar with all Chance to Block nuances!

Credits

Written by Teo1904
Reviewed by MacroBioBoi