The game determines the success of various actions by rolling dice for you and for other creatures in the game. The result of a die roll or dice roll is often modified by bonuses and penalties. Characters that are very skilled, use powerful items to enhance their abilities, or are under the effects of ability-enhancing effects (such as from spells or potions) will tend to roll higher numbers. Characters that are unskilled, don't have access to good equipment, or are under the effect of negative conditions, will instead tend to roll lower numbers.
Karmic Dice
In Baldur's Gate 3 you can enable the option to use so-called Karmic Dice. This means that the game will avoid frustrating streaks of very low rolls in a row, and perhaps overly lucky streaks of very high rolls in a row. The exact algorithm is not presently known and may be changed between versions of the game.
Types of rolls
Beyond the general principles explained above, the details of rolls depend on the type of roll that is being made. Following are the types of rolls in the game.
Attack Roll
When a creature attacks another, it rolls a d20. The result is modified by its Ability Score Modifier and Proficiency Bonus. If the result matches or exceeds the Armor Class of the target, then the attack is successful. Otherwise, it's a failure; this could mean the attack was a miss, failed to hurt the target due to its armor, or the target was able to dodge or parry.
Attacks done with Weapons always use an Attack Roll to determine success. Some spells also use an Attack Roll to determine whether they hit their intended target (such as Fire Bolt or Eldritch Blast), though other spells hit the target automatically (such as Magic Missile or Fireball). A spell that hits its target automatically may allow the target to make a Saving Throw instead.
The Ability Score used for the Modifier depends on the type of attack that's being made. Melee and ranged weapon attacks use Strength or Dexterity, depending on the weapon. For spells, the Ability Score used for the Modifier generally depends on the class of the caster:
| Intelligence | Wisdom | Charisma |
|---|---|---|
|
The Attack Roll should not be confused with the Damage Roll, which instead determines the amount of damage done to a target by a successful attack.
Damage Roll
When an attack is successful, the damage it does to the target, in terms of hit-points, is determined through the Damage Roll. This can involve any type and number of dice. For example, a successful hit with a Dagger will lead to a d4 being rolled to determine the damage, whereas a successful attack with a Greatsword will lead to two d6 being rolled (referred to as 2d6) for a total damage of 2 to 12.
Note that due to the mathematics of dice rolls, the difference between 1d8 and 2d4 is more than just a higher minimum value 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 than a total value of 8. This is most easily explained with a table of the possible outcomes:
| First roll | Second roll | Total value |
|---|---|---|
| 1 | 1 | 2 |
| 1 | 2 | 3 |
| 1 | 3 | 4 |
| 1 | 4 | 5 |
| 2 | 1 | 3 |
| 2 | 2 | 4 |
| 2 | 3 | 5 |
| 2 | 4 | 6 |
| 3 | 1 | 4 |
| 3 | 2 | 5 |
| 3 | 3 | 6 |
| 3 | 4 | 7 |
| 4 | 1 | 5 |
| 4 | 2 | 6 |
| 4 | 3 | 7 |
| 4 | 4 | 8 |
Notice how often the 5 appears in the possibilities for the total value (4 out of 16) 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 6.125% chance of resulting in 8 points of damage. Meanwhile, the 1d8 roll actually has a higher chance of maximum damage, since 1 out of 8 rolls (12.5%) will be an 8.
Saving Throw
Various types of danger can be avoided by making a Saving Throw, also called making a save. The creature rolls a d20, and adds its Ability Score Modifier and Proficiency Bonus. The source of danger determines the Difficulty Class of the save as well as the Ability Score that determines the Modifier. If the result of the roll matches or exceeds the Difficulty Class, the save succeeds.
A successful save could mean completely avoiding negative effects, or it could mean halving the damage received. For example, successfully saving against a spike trap could mean that you take no damage at all because you've successfully evaded the spikes. On the other hand, if a Fireball is cast on you, be it by a spellcaster or a magical trap, then a successful Saving Throw will merely cut the damage in half. Some effects don't allow for a Saving Throw at all, for example the damage taken from Magic Missile.
Depending on the Ability Score used for the Modifier, a Saving Throw may be referred to as a Strength Saving Throw, Dexterity Saving Throw, Constitution Saving Throw, and so on.
Ability Check
Various actions, other than attacking or making a save, still require the creature to make an attempt that may fail. The creature rolls a d20, and adds its Ability Score Modifier and possibly a Proficiency Bonus. The attempted action has a specific Difficulty Class which the result of the roll must match or exceed.
Ability Checks can be based purely on an Ability Score, in which case they can only benefit from the Ability Score Modifier, but not any Proficiency Bonus. More commonly however, the check will be related to a specific Skill, which not only determines the Ability Score used for the Modifier, but also lets the creature use its Proficiency Bonus if it happens to be Proficient in that particular Skill.
For example, when a trap is near a creature, the game rolls a Perception Check to determine whether the creature notices the existence of the trap. (This is not to be confused with making a Saving Throw after the trap is activated.) Perception is based on Wisdom, so a creature with a high Wisdom score will gain a bonus. If the creature doesn't gain any bonus from Wisdom, it could still gain a bonus from being Proficient in the Perception Skill. If the creature both has high Wisdom and is also proficient in Perception, it will gain both bonuses.
Following is a table categorizing the various Skills based on the Ability Score which they use for the Ability Score Modifier.
| Strength | Dexterity | Intelligence | Wisdom | Charisma |
|---|---|---|---|---|
|
|
|
|
|
(There are no Skills based on Constitution.)
Modifiers
Rolls can be affected by various bonuses and penalties. These can take the form of adding or subtracting a value from the result, or requiring two rolls instead of one and taking the lower or higher of the two values.
Advantage / Disadvantage
In various situations, a creature can have Advantage or Disadvantage on an Attack Roll, Saving Throw, or Ability Check.
Advantage simply means that you make the roll twice, and use the higher result. Disadvantage simply means you make the roll twice, and use the lower result.
Advantage and Disadvantage can cancel each other out. However, they cannot stack, meaning that you never roll more than twice.
Examples of situations that grant Advantage:
- Having the higher ground while making an attack
- Being unseen by the enemy while making an attack
- Various spells and abilities that grant Advantage
Examples of situations that grant Disadvantage:
- Trying to attack an enemy on higher ground
- Trying to attack an enemy obscured by darkness
- Various spells and abilities that grant Disadvantage
Ability Score Modifier
A creature's Ability Scores can modify the result of rolls depending on how high or low the score is. (It can be negative if the score is very low.)
| Score | Modifier |
|---|---|
| 1 | -5 |
| 2-3 | -4 |
| 4-5 | -3 |
| 6-7 | -2 |
| 8-9 | -1 |
| 10-11 | +0 |
| 12-13 | +1 |
| 14-15 | +2 |
| 16-17 | +3 |
| 18-19 | +4 |
| 20-21 | +5 |
| 22-23 | +6 |
| 24-25 | +7 |
| 26-27 | +8 |
| 28-29 | +9 |
| 30 | +10 |
Which Ability Score is used to determine the Modifier depends on the roll that's being made.
For Attack Rolls
Weapon attacks will generally use Strength or Dexterity, depending on the weapon. For example, a Greatsword will always use Strength, and a Longbow will always use Dexterity. For some weapons, the higher of two Ability Scores can be chosen for the roll. This includes melee weapons with the Finesse property such as Rapier, and ranged weapons with the Thrown property such as Handaxe.
Spell attacks will use an Ability Score depending on the Class of the creature making it; see table above, under the section #Attack Roll.
For Saving Throws
For saves against specific spells and conditions, the spell or condition in question determines which Ability Score is used to make the save. For example, the Web spell requires you to make a Dexterity save, whereas Crown of Madness requires a Wisdom save. As with most spells and effects related to poison, Poison Spray requires a Constitution saving throw.
For Ability Checks
Which Ability Score is used for an Ability Check depends on the category or type of Ability Check, such as Athletics, Sleight of Hand, History, Perception, Deception, and so on. See the table above, under the section #Ability Check, for the different categories and which Ability Score they use for the Modifier.
Proficiency Bonus
Creatures can have Proficiency in a number of talents, which grant them bonuses on various rolls. Proficiencies can be granted by a creature's Background, Race, Class, and Feats chosen when leveling up.
| Level | Proficiency Bonus |
|---|---|
| 1 to 4 | + 2 |
| 5 to 8 | + 3 |
| 9 to 12 | + 4 |
| 13 to 16 | + 5 |
| 17 to 20 | + 6 |
For Attack Rolls
Attack Rolls made with Weapons can benefit from Proficiency with the type of weapon that's being used. This kind of Proficiency can be granted by the creature's Race, Class, or Feats chosen when leveling up.
Weapon Proficiency may apply to a specific type of weapon, like Longswords, or a category of weapons, like Martial Weapons. For example, all High Elves and Wood Elves, regardless of their class, have a specific Proficiency in Longswords, Shortswords, Longbows, and Shortbows. On the other hand, Fighters have Proficiency in the entire categories of both Simple and Martial Weapons. Clerics have Proficiency in the category of Simple Weapons, whereas Wizards only have Proficiency in Quarterstaves, Daggers, and Light Crossbows.
Attack Rolls made for spells benefit from Proficiency in spell casting, which all creatures capable of casting spells have. The creature could have spell casting capabilities due to its Class, or from a Feat it chose when leveling up.
The lack of Proficiency in spell casting becomes apparent when you give a scroll such as Scroll of Guiding Bolt to a character that can't otherwise cast spells. Since Guiding Bolt uses an Attack Roll, but the character is not proficient in spell casting, they will have a lower chance to hit targets with the Guiding Bolt.
For Saving Throws
You can have Proficiency in a specific kind of Saving Throw, like Strength Saving Throw, Dexterity Saving Throw, and so on.
There is no other categorization of Saving Throws.
For Ability Checks
You can have Proficiency in a Skill, which may be used for an Ability Check:
- Athletics
- Acrobatics
- Sleight of Hand
- Stealth
- Arcana
- History
- Investigation
- Nature
- Religion
- Animal Handling
- Insight
- Medicine
- Perception
- Survival
- Deception
- Intimidation
- Performance
- Persuasion
Note that an Ability Check may be based directly on an Ability Score rather than a Skill, in which case no Proficiency Bonus is possible.