When the outcome of an action is uncertain, the game uses a d20 roll to determine success or failure. These rolls are called D20 Tests, and they come in three kinds: ability checks, saving throws, and attack rolls. They follow these steps:
1: Roll 1d20. You always want to roll high. If the roll has Advantage or Disadvantage (described later in this chapter), you roll two d20s, but you use the number from only one of them—the higher one if you have Advantage or the lower one if you have Disadvantage.
2: Add Modifiers. Add these modifiers to the number rolled on the d20:
3: Compare the Total to a Target Number. If the total of the d20 and its modifiers equals or exceeds the target number, the D20 Test succeeds. Otherwise, it fails. The Dungeon Master determines target numbers and tells players whether their rolls are successful. The target number for an ability check or a saving throw is called a Difficulty Class (DC). The target number for an attack roll is called an Armor Class (AC), which appears on a character sheet or in a stat block (see the rules glossary).
An ability check represents a creature using talent and training to try to overcome a challenge, such as forcing open a stuck door, picking a lock, entertaining a crowd, or deciphering a cipher. The DM and the rules often call for an ability check when a creature attempts something other than an attack that has a chance of meaningful failure. When the outcome is uncertain and narratively interesting, the dice determine the result.
An ability check is named for the ability modifier it uses: a Strength check, an Intelligence check, and so on. Different ability checks are called for in different situations, depending on which ability is most relevant. See the Ability Check Examples table for examples of each check’s use.
| Ability | Make a Check To … |
|---|---|
| Strength | Lift, push, pull, or break something |
| Dexterity | Move nimbly, quickly, or quietly |
| Constitution | Push your body beyond normal limits |
| Intelligence | Reason or remember |
| Wisdom | Notice things in the environment or in creatures’ behavior |
| Charisma | Influence, entertain, or deceive |
Add your Proficiency Bonus to an ability check when the DM determines that a skill or tool proficiency is relevant to the check and you have that proficiency. For example, if a rule refers to a Strength (Acrobatics or Athletics) check, you can add your Proficiency Bonus to the check if you have proficiency in the Acrobatics or Athletics skill. See “Proficiency” later in this chapter for more information about skill and tool proficiencies.
The Difficulty Class of an ability check represents the task’s difficulty. The more difficult the task, the higher its DC. The rules provide DCs for certain checks, but the DM ultimately sets them. The Typical Difficulty Classes table presents a range of possible DCs for ability checks.
| Task Difficulty | DC |
|---|---|
| Very easy | 5 |
| Easy | 10 |
| Medium | 15 |
| Hard | 20 |
| Very hard | 25 |
| Nearly impossible | 30 |
A saving throw—also called a save—represents an attempt to evade or resist a threat, such as a fiery explosion, a blast of poisonous gas, or a spell trying to invade your mind. You don’t normally choose to make a save; you must make one because your character or a monster (if you’re the DM) is at risk. A save’s result is detailed in the effect that caused it. If you don’t want to resist the effect, you can choose to fail the save without rolling.
Saving throws are named for the ability modifiers they use: a Constitution saving throw, a Wisdom saving throw, and so on. Different saving throws are used to resist different kinds of effects, as shown on the Saving Throw Examples table.
| Ability | Make a Save To … |
|---|---|
| Strength | Physically resist direct force |
| Dexterity | Dodge out of harm’s way |
| Constitution | Endure a toxic hazard |
| Intelligence | Recognize an illusion as fake |
| Wisdom | Resist a mental assault |
| Charisma | Assert your identity |
You add your Proficiency Bonus to your saving throw if you have proficiency in that kind of save. See “Proficiency” later in this chapter.
An attack roll determines whether an attack hits a target. An attack roll hits if the roll equals or exceeds the target’s Armor Class. Attack rolls usually occur in battle, described in “Combat” later in this chapter, but the DM might also ask for an attack roll in other situations, such as an archery competition.
The Attack Roll Abilities table shows which ability modifier to use for different types of attack rolls.
| Ability | Attack Type |
|---|---|
| Strength | Melee attack with a weapon or an Unarmed Strike (see "Rules Definitions") |
| Dexterity | Ranged attack with a weapon |
| Varies | Spell attack (the ability used is determined by the spellcaster’s spellcasting feature, as explained in chapter 7 "Spells") |
Some features let you use different ability modifiers from those listed. For example, the Finesse property (see chapter 6 "Weapons") lets you use Strength or Dexterity with a weapon that has that property.
You add your Proficiency Bonus to your attack roll when you attack using a weapon you have proficiency with, as well as when you attack with a spell. See “Proficiency” later in this chapter for more information about weapon proficiencies.
A creature’s Armor Class represents how well the creature avoids being wounded in combat. The AC of a character is determined at character creation (see chapter 2 "Creating a Character"), whereas the AC of a monster appears in its stat block.
Calculating AC. All creatures start with the same base AC calculation:
Base AC = 10 + the creature’s Dexterity modifier
A creature’s AC can then be modified by armor, magic items, spells, and more.
Only One Base AC. Some spells and class features give characters a different way to calculate their AC. A character with multiple features that give different ways to calculate AC must choose which one to use; only one base calculation can be in effect for a creature.
If you roll a 20 on the d20 (called a “natural 20”) for an attack roll, the attack hits regardless of any modifiers or the target’s AC. This is called a Critical Hit (see “Combat” later in this chapter). If you roll a 1 on the d20 (a “natural 1”) for an attack roll, the attack misses regardless of any modifiers or the target’s AC.
Sometimes a D20 Test is modified by Advantage or Disadvantage. Advantage reflects the positive circumstances surrounding a d20 roll, while Disadvantage reflects negative circumstances. You usually acquire Advantage or Disadvantage through the use of special abilities and actions. The DM can also decide that circumstances grant Advantage or impose Disadvantage.
When a roll has either Advantage or Disadvantage, roll a second d20 when you make the roll. Use the higher of the two rolls if you have Advantage, and use the lower roll if you have Disadvantage. For example, if you have Disadvantage and roll an 18 and a 3, use the 3. If you instead have Advantage and roll those numbers, use the 18.
If multiple situations affect a roll and they all grant Advantage on it, you still roll only two d20s. Similarly, if multiple situations impose Disadvantage on a roll, you roll only two d20s.
If circumstances cause a roll to have both Advantage and Disadvantage, the roll has neither of them, and you roll one d20. This is true even if multiple circumstances impose Disadvantage and only one grants Advantage or vice versa. In such a situation, you have neither Advantage nor Disadvantage.
When you have Advantage or Disadvantage and something in the game lets you reroll or replace the d20, you can reroll or replace only one die, not both. You choose which one. For example, if you have Heroic Inspiration (see the sidebar) and roll a 3 and an 18 on an ability check that has Advantage or Disadvantage, you could expend your Heroic Inspiration to reroll one of those dice, not both of them.
Heroic Inspiration
Sometimes the DM or a rule gives you Heroic Inspiration. If you have Heroic Inspiration, you can expend it to reroll any die immediately after rolling it, and you must use the new roll.
Only One at a Time. You can never have more than one instance of Heroic Inspiration. If something gives you Heroic Inspiration and you already have it, you can give it to a player character in your group who lacks it.
Gaining Heroic Inspiration. Your DM can give you Heroic Inspiration for a variety of reasons. Typically, DMs award it when you do something particularly heroic, in character, or entertaining. It’s a reward for making the game more fun for everyone playing. Other rules might allow your character to gain Heroic Inspiration independent of the DM’s decision. For example, Human characters start each day with Heroic Inspiration.