Editing Dice rolls

'''Dice rolls''' are a central game mechanic in ''Baldur's Gate 3''. Dice are rolled to determine the outcome of variety of situations, such as whether or not a character will succeed at using a particular skill, or if an attack will land and how much damage it will do.

Dice are notated with a ''d'' followed by the number of sides on that specific dice: {{hlist|

The number of dice to be rolled is notated immediately before the ''d''. Any applicable '''[[#Modifiers|modifiers]]''' for the roll are given as an addition (if it is a '''bonus''') or subtraction (if is a '''penalty''') after the dice notation. When a single twenty sided dice (d20) is rolled with no modifiers, it is notated as {{InfoBlob|1d20}}. When two six-sided dice (d6) are rolled with a modifier of +3, the roll is notated as {{InfoBlob|2d6+3}}.

The range of potential results is often given in parentheses, especially for [[#Damage rolls|damage rolls]]. For example, a single dart from a {{SAI|Magic Missile|h=20px}} spell does {{InfoBlob|1d4+1 (2-5) Force damage}}. This means rolling 1d4 and adding 1 to the result, giving a possible total of 2 to 5 points of damage.

A number of '''modifiers''' are potentially added to dice rolls. Modifiers are either '''bonuses''' which add to the result, or '''penalties''' which are subtracted from it. A roll may have bonuses and/or penalties from multiple sources; in such cases they are added together and expressed as a single modifier. For example, a d20 roll with a bonus of +5 and a penalty of -2 would be expressed as {{InfoBlob|1d20+3}}.

; Ability score modifiers : Most rolls have an associated [[ability]], and creatures add their corresponding ability score modifier to the outcome of rolls they make.

; Proficiency bonus : Creatures add their proficiency bonus to any attack rolls, ability checks, or saving throws that they make using weapons, skills, or saves that they are proficient in, as well as to all attack rolls made during spell attacks.

; Additional modifiers : Some [[features]] and [[conditions]] add additional modifiers to save DCs and the results of rolls, such as [[Shillelagh]], which allows the caster to add their spellcasting ability modifier to their attack and damage rolls, instead of Strength or Dexterity.

 

When a creature forces an opponent to make a [[#Saving throw|saving throw]] against a spell the creature has cast or action they have taken, the applicable modifiers are added to the creature's save DC instead.

Whenever a creature attempts an action that has a chance of failure, it rolls a twenty-sided die (d20) against a target number to determine whether the attempt was a success or a failure, and add any applicable modifiers. If the result is equal to or exceeds the target number, the attempt was successful. If the result was lower than the target number, or if the creature rolled a 1, the attempt failed.

These attempts are categorized either as attack rolls – which are rolled against the target's [[Armour Class]] (AC), as ability checks – which are rolled against the check's Difficulty Class (DC), or as saving throws – which are rolled against a save DC:

; Attack rolls : When a creature attacks a target, it makes an attack roll against the target's AC to determine whether the attack is a hit or a miss. If the attack is a hit, it generally deals damage, and the attacker rolls for damage. Creatures generally make their attacks with their equipped [[weapon]] (including unarmed), but some [[spells]] – such as a [[Warlock]]'s [[Eldritch Blast]] – require the caster to make spell attack rolls.

; Saving throws : Traps, spells, conditions, and other sources of harm may allow a creature a chance to avoid or reduce their effect, known as a saving throw or ''save''. To attempt a save, a creature rolls a d20 against a target save DC.

The number is determined by the the task attempted – or in the case of saves – the spell, condition, or action that has to be overcome.

Rolling a 1 or 20 on a d20 roll is referred to as a ''natural 1'' or ''natural 20''. When making an attack roll or ability check, rolling a natural 1 is always an automatic failure, while a natural 20 is always an automatic success, regardless of the final result after modifiers are applied. Saving throws attempted during dialogue, and death saving throws, can also roll natural 1s and 20s.

Unlike attack rolls and ability checks, saving throws are not guaranteed to fail or succeed when the d20 result is either a natural 1 or 20 respectively, unless they occur during dialog.

A [[List of sources of advantage|number of situations and conditions]] give creatures advantage or disadvantage on d20 rolls. A creature that makes a roll with advantage rolls two d20 dice separately, and uses the higher of the two results. If they have disadvantage, they choose the lower of the two.

Creatures receive no additional benefit or penalty from having multiple sources of advantage or disadvantage on a dice roll, and still only roll twice. Likewise, creatures that have {{em|both}} advantage and disadvantage on a roll only roll a single die, even if they have multiple sources of either.

Ability checks are dice rolls made to determine whether a creature succeeds or fails at a task. They are rolled against the task's Difficulty Class (DC), which is generally predetermined by the game. Each ability check is made using one of the six [[abilities]] in the game, and creatures add an ability's corresponding ability score modifier to the results of ability checks they make.

Characters can also have expertise in a skill, which allows them to add {{em|double}} their proficiency bonus when making a corresponding ability check. While it is possible to have proficiency {{em|and}} expertise in a skill at the same time, they do not stack. Some sources of expertise do, however, require the character to already be proficient in a skill.

: Some ability checks are automatic. For example, when a creature approaches an inactive trap, the game rolls a [[Perception]] ability check to determine whether the creature notices the trap. Perception is a Wisdom skill, so the character adds their Wisdom modifier and, if proficient in Perception, their proficiency bonus to the ability check. Once the trap is discovered, the character can interact with it to attempt to [[Disarm]] it, which requires a successful [[Sleight of Hand]] check, a Dexterity skill.

Saving throws represent a creature’s attempt to “'''save'''” themselves from harm. Spells and actions taken by other creatures frequently allow their targets to attempt a save, as do hazards like [[traps]] and [[surface]]s. Each save has an associated ability – referred to using terms like '''Strength saving throw''' or '''Dexterity save''' – and a save DC that creatures attempting to save roll against. When attempting a save, a creature adds an ability score modifier corresponding to that save's associated ability, and if they are proficient in saves made using that ability, they add their proficiency bonus as well.

While the result of an attempted saving throw is always binary – it is either a success or a failure – the exact outcome of a successful save depends on the effect in question. Typically, the damage or conditions inflicted by the associated effect will be reduced in severity, and sometimes negated entirely.

A [[List of features and items that affect saving throws|number of features]] affect saving throws, and some races have advantage on certain saves.

All classes give save proficiency with two abilities. Though when multiclassing, only the '''first''' class taken gives its save proficiencies. An additional save proficiency can be gained by taking the [[Resilient]] feat.

 

; Spell save DC : The Difficulty Class of a spell that can be saved against is determined through the following formula:

: Certain [[conditions]] and [[List of Equipment that Affect Spell DC|equipment]] worn by the caster can also affect their Spell Save DC.

; Weapon save DC: Most weapons allow proficient users to perform special "weapon actions", which are typically limited to once per short rest (e.g. [[Backbreaker]]). These actions often include the chance to inflict a condition on the target, and these conditions require the target to attempt a Save to avoid them. Each weapon action can grant its own inherent bonus to DC that isn't listed anywhere, but is frequently +2. The Difficulty Class of saves allowed by weapon actions is calculated as follows:  

:: {{InfoBlob|1=Weapon Action DC = 8 + proficiency bonus + [[Strength]] or [[Dexterity]] modifier + inherent weapon action bonus DC}}

: Certain weapon actions, notably [[Concussive Smash]], instead allow the acting creature to either use their Spell Save DC or weapon action DC with a +2 bonus, whichever is higher.

In the case of threats that don't originate from a spellcaster, such as a trap or a poisonous apple, the game sets the DC based on how serious the threat is intended to be. For example, a rather ineffective trap might have a DC of just 5, whereas an effective trap could have a DC of 15. A slightly spoiled tart could impose a DC 5 Constitution save when eaten, whereas a potent venom from a snake could impose a DC 15 Constitution save on the victim.

Death saving throws are a special type of saving throw made by playable characters after they have been {{cond|Downed}}. Death saves are made once per turn while the character remains Downed. If a Downed character receives damage from any source that isn't a critical hit, they automatically fail one death saving throw. A critical hit against a Downed character results in 2 failed saves. Melee attacks against a Downed target are always classified as a critical hit.

 

Three successful saves will let a creature stabilize, no longer needing to make death saves to survive, and three failures will lead to the creature becoming {{cond|Dead}}.  

Death saving throws are not associated with an ability score and so don't get any modifiers, nor do they benefit from the proficiency bonus. They only benefit from bonuses that apply to all saving throws (such as {{SAI|Bless}}) or specifically to death saves (such as [[Family Ring]]). Death saves are always DC 10. A character dies when three failures are accumulated, or stabilizes when three successes are accumulated, whichever happens first.

 

Death saving throws can be critical failures and critical successes. A natural 1 rolled for a death save will add ''two'' failures to a character's death save count, while a natural 20 will immediately stabilize the character regardless of their current death save count.

If the result of the attack roll is equal to or higher than the target's Armour Class (AC), the attack ''hits'', and the attacker rolls for damage. If the result is lower than the target's AC, the attack ''misses''.

* Unarmed attacks, and attacks made with melee weapons and thrown weapons generally add the attacking creature's Strength modifier.

* If the weapon has the [[Finesse]] property, attacks with it add either the attacker's Strength or Dexterity modifier, whichever is higher.

* Unarmed attacks may use the attacker's Dexterity modifier if they have certain features like [[Martial Arts: Dextrous Attacks|Dextrous Attacks]] from the [[Monk]] class.

If the attacker is proficient with the weapon they are wielding, or if the attack is a spell attack or unarmed attack, they also add their proficiency bonus.

When a creature rolls a natural 20 on an attack roll, the attack is a [[critical hit]]''.'' Critical hits automatically land regardless of the target's AC, and the attacker also rolls twice the normal number of dice to determine damage dealt, including additional dice such as those from smites or combat maneuvers. Modifiers and bonuses – including the creature's relevant ability score modifier and proficiency bonus – are not doubled.

Some [[feats]], [[Classes|class features]], and [[items]] [[Critical Hit threshold reduction|reduce]] the critical hit threshold by 1, allowing the creature to land critical hits by rolling either 19 or 20 on attack rolls. Multiple sources of this effect stack, allowing the critical hit threshold to go even lower than 19.

Armour Class (AC) is a measurement of how difficult a creature is to be hit by an attack. In order to successfully hit a creature, the results of an [[Attack roll|attack roll]] must be equal to or greater than the target's Armour Class. AC can be increased by equipping [[Armour|armour]] and [[Shields|shields]], by selecting certain [[Feats|feats]] when leveling up, or utilizing certain [[Spells|spells]].

The formula that determines AC when wearing Armour in the torso slot is:

: {{InfoBlob|Torso armor AC + [[Dexterity|Dexterity modifier]] + shield bonus + other bonuses and penalties}}

The AC bonus from Dexterity is typically capped at +2 when wearing [[Armour#Medium armour|medium armour]]{{note|The [[Medium Armour Master]] feat increases the cap from +2 to +3.}}{{note|A few rare armours have an "Exotic Material" trait that allow the wearer to get the full Dexterity bonus to AC. These include [[Yuan-Ti Scale Mail]], [[Unwanted Masterwork Scalemail]], [[Sharpened Snare Cuirass]], and [[Armour of Agility]].}}, and is reduced to zero when wearing [[Armour#Heavy armour|heavy armour]].

Most [[Shields]] grant +2 AC.

Other bonuses include things like the [[Fighting style|Defense]] fighting style, which grants +1 AC while wearing armor, and the [[Cloak of Protection]], which grants +1 AC at all times. Bonuses to AC stack with each other.

 

Unarmoured creatures may use a different formula if they have certain features. Creatures always use whichever formula they have access to that would result in the highest AC. Alternative formulas are only used if no items marked "Light Armor", "Medium Armor", or "Heavy Armor" are being worn in any equipment slot.

: {{InfoBlob|10 + Constitution modifier + Dexterity modifier + shield bonus + other bonuses and penalties}}

: {{InfoBlob|10 + Wisdom modifier + Dexterity modifier + other bonuses and penalties}}

The base damage dealt by a [[weapons|weapon]], [[spells|spell]], class action, or condition is usually determined by a ''damage roll''. Damage rolls always have an associated [[damage type]] that is given following the dice notation, e.g. {{DamageText|1d4|Piercing}}.

Modifiers added to damage rolls are only added {{em|once}} per source, even if multiple dice are rolled.

* When making weapon attacks, the attacking creature usually adds the ability score modifier that they added to the attack roll.

* Ability score modifiers are not normally added to damage rolls dealt by spells or spell attacks, unless specifically stated otherwise in the spell's description, or if enabled by some feature, such as {{SAI|Agonising Blast|h=20px}}.

Proficiency bonuses are {{em|not}} added to damage rolls unless the attack being used (e.g. [[Shadowsoaked Blow]]) says so.

; Healing : [[Healing]] restores a target's [[hit points]] in a similar manner to damage rolls. Healing rolls may also add modifiers, but there's no general rule for this; any bonuses are determined by the source of the healing. For example, a [[Potion of Healing]] restores {{DamageText|2d4+2|Healing}}. There are many magic items, class features, and other effects which also provide bonuses to healing, for example the {{Class|Life Domain}}'s {{SAI|Disciple of Life}} feature.

When the Karmic Dice option is enabled (it is by default), the game will avoid streaks of low rolls.  

To illustrate this, if a defender has 15 AC and 10 HP, and the attacker has +5 to attack rolls, and deals 2 damage per attack, the defender would on average survive for 10 turns because the attack has a 50% chance to hit against 15 AC.

If the defender's AC was increased to 16 (chance to hit drops to 45%), they would instead survive for an average of 11.1 rounds (an 11% increase in effectiveness).

Meanwhile, if the defender starts with 19 AC (30% chance to be hit), they would survive for an average of 16.66 rounds. But if their AC was increased to 20 (25% chance to be hit), they would be able to survive for an average of 20 rounds (a 20% increase in effectiveness).

The difference between 25 and 24 is even greater, granting a {{em|200%}} increase in effectiveness (50 vs 100 rounds).

Note that due to the mathematics of dice rolls, the difference between, say, 1d8 and 2d4 is more than just the higher minimum value of 2 on the 2d4 roll. With the d8, you have an equal chance of getting, say, a 5 and an 8.  On the other hand, the 2d4 roll is statistically more likely to lead to a total value of 5, rather than a total value of 8. This is most easily explained with a table of all possible outcomes:

Notice how often the 5 appears in the possibilities for the '''total value''' (4 out of 16 possibilities) vs. how often the 8 appears (1 out of 16).  This means a 2d4 roll has a 25% chance of resulting in 5 points of damage, but only a 6.25% chance of resulting in 8 points of damage.  Meanwhile, the 1d8 roll actually has a higher chance of resulting in the maximum damage value of 8, since 1 out of 8 possibilities (12.5%) result in an 8. However, the average roll of 2d4 is 5 damage, while the average roll of 1d8 is only 4.5. Therefore, 2d4 is generally more consistent in damage output and will result in higher rolls in the long run.  

|9||60% ||84%|| 36%

==== Effects of advantage on the average of dice rolls ====

The formula to calculate the expected value, {{math|\mathbb{E}[x]}}, of a variable {{math|x}} is equal to the sum of every possible value of {{math|x}} multiplied by the chance for {{math|x}} to have that value.  

 

When we apply this expression to a d20, the results is that having advantage is equivalent to an average bonus of +3.325.

When making an ability check, attack roll, or saving throw, a 1 or a 20 will {{em|always}} be treated as a critical failure or success, respectively, regardless of the results after any potential modifiers are added. On a dice roll without advantage or disadvantage, this effectively means there is a {{math|1/20}} (or 5%) chance of either a critical success or failure.

Having advantage or disadvantage can drastically increase or reduce the chance of critical successes and Failures. For example, when rolling with advantage, the only way to get a Critical Failure is to roll {{em|two}} 1s at the same time. The odds of this result is {{math|1=1/20 \cdot 1/20 = 1/400}} (or 0.25%). Conversely, rolling a Critical Success is far more likely - out of the 400 possible dice roll outcomes,  39 will result in a 20 (rolling 20 on the first die and 1, 2, 3, ... 20 on the second die, plus rolling 20 on the second die and 1, 2, 3, ... 20 on the first die, minus one so that the result of two 20s is not doubly-counted). The odds of this result is {{math|39/400}} (or 9.75%). The opposite is true for rolling with Disadvantage: a Critical Success has a 0.25% chance and a Critical Failure has a 9.75% chance.

Effectively, rolling with advantage means that critical failures are ''20 times {{em|less}} likely'', and critical successes are almost {{em|twice}} as likely, while the inverse is true for disadvantage.