More actions
The game determines the success of various actions by rolling dice for you and for other creatures in the game. The result of a 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.
Types of rolls
Beyond the general principles explained above, the details of a dice roll depend on the type of roll that is being made. Following are the types of dice 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 Proficiency Bonus. Every attempted action has a specific Difficulty Class which the result of the roll must match or exceed so as to succeed. There are also different types of Ability Checks, determining which Ability Score is used to determine the Modifier.
For example, when a trap is near a creature, the game rolls a Perception Check for it, 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.) Once the trap is detected, the creature may attempt to disarm it, which requires a Sleight of Hand Check.
The different kinds of checks benefit from different abilities. Following is a table of all types of Ability Check, sorted by the Ability Score whose modifier the check uses:
| Strength | Dexterity | Intelligence | Wisdom | Charisma |
|---|---|---|---|---|
|
|
|
|
|
(There are no Ability Checks using Constitution.)
Modifiers
Dice 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
To do.
Ability Score Modifier
To do.
Proficiency Bonus
To do.