The term d20 Test encompasses the three main d20 rolls of the game: Ability Checks, Attack Rolls, and Saving Throws. If something in the game affects d20 Tests, it affects all three of those rolls.
The DM decides whether a d20 Test is warranted in any given circumstance—when the outcome is uncertain, the dice are used to determine the results—and then sets the difficulty of the task which is represented by a Difficulty Class. The more difficult a task, the higher its DC. A d20 Test must have a target number no less than 5 and no greater than 30. The table below offers a good rule of thumb for appropriate Difficulty Classes based on how easy the task is assumed to be:
| Task Difficulty | DC |
| Very easy | 5 |
| Easy | 10 |
| Medium | 15 |
| Hard | 20 |
| Very hard | 25 |
| Near impossible | 30 |
Success without Rolling
As stated above, d20 tests should be made only when the outcome is uncertain, thus the DM should only call for a roll when an action has a chance of failure. Rolling dice is fun but a series of bad rolls can leave an adventurer feeling distinctly unheroic, or stop an adventure moving forward at all! When stakes are low, allowing a character to succeed on tasks they’re good at drives play forward and strengthens a character’s identity at the same time.
When deciding whether a roll is necessary, consider the character’s abilities and skills (see Passive Checks below). For example, a PC with a high Strength score might automatically open a stuck door, one proficient in Survival might automatically spot horse tracks in the snow, or someone proficient in Religion could naturally recognize a holy symbol of a prominent god and know the god’s domains. Also take into account the character’s actions. If a player describes their character pulling aside a tapestry, they don’t need to roll to find the concealed artifice hidden behind it.
It’s also worth noting that whenever an action can’t succeed at all that a dice roll is also inappropriate—when a character attempts the impossible the only possible outcome is failure.
In short, if there isn’t a chance of success or failure don’t call for a roll of the dice.
When determining what to roll when making a d20 Test, the DM should consider the intent of the action being undertaken and the task to be used to accomplish the action. In many cases, the answer to these questions will be self evident:
When making an Attack Roll, the player or monster is attempting to use weaponry, spells, or raw force to secure an outcome, which is typically causing harm to another creature or object. This can also be modified by a character or monster's proficiency bonus if they have a relevant proficiency with the weapon or method they are utilizing to attack their target.
When making a Saving Throw, the player or monster is attempting to resist an outside force acting against them, such as a spell, a trap, a poison, a disease, or a similar threat. Normally, you do not decide to make a saving throw. You are forced to make one because your character or a monster is at risk of external harm.
Characters have a proficiency bonus determined by level. Monsters also have this bonus, which is incorporated in their stat blocks. This bonus is used, as appropriate, when making d20 Tests. In order to add your Proficiency Bonus to a d20 Test, a character or monster must have a relevant proficiency, such as having training in a particular skill—like Athletics or Religion—or training with a particular weapon as noted above.
| Proficiency Bonus by Level | |||
| Level | Bonus | Level | Bonus |
| 1 | +2 | 11 | +4 |
| 2 | +2 | 12 | +4 |
| 3 | +2 | 13 | +5 |
| 4 | +2 | 14 | +5 |
| 5 | +3 | 15 | +5 |
| 6 | +3 | 16 | +5 |
| 7 | +3 | 17 | +6 |
| 8 | +3 | 18 | +6 |
| 9 | +4 | 19 | +6 |
| 10 | +4 | 20 | +6 |
Your proficiency bonus can’t be added to a single die roll or other number more than once. For example, if two different rules say you can add your proficiency bonus to a Wisdom Saving Throw, you nevertheless add the bonus only once when you make the save.
Occasionally, your proficiency bonus might be multiplied or divided (doubled or halved, for example) before you apply it. For example, the rogue’s Expertise feature doubles the proficiency bonus for certain ability checks. If a circumstance suggests that your proficiency bonus applies more than once to the same roll, you still add it only once and multiply or divide it only once.
By the same token, if a feature or effect allows you to multiply your proficiency bonus when making an ability check that wouldn’t normally benefit from your proficiency bonus, you still don’t add the bonus to the check. For that check your proficiency bonus is 0, given the fact that multiplying 0 by any number is still 0. For instance, if you lack proficiency in the History skill, you gain no benefit from a feature that lets you double your proficiency bonus when you make Intelligence (History) checks.
In general, you don’t multiply your proficiency bonus for attack rolls or saving throws. If a feature or effect allows you to do so, these same rules apply.
To make a d20 Test, the player or DM rolls a d20 and adds the relevant ability modifier, plus their proficiency bonus if applicable, and then compare the total to the DC. If the total equals or exceeds the DC, the d20 Test is a success—the creature overcomes the challenge at hand. Otherwise, it’s a failure, which means the character or monster makes no progress toward the objective or makes progress combined with a setback determined by the DM.
Though uncommon, there are occasionally situations where other external factors might add or subtract from a d20 Test, just like your Ability Score Modifier or your Proficiency Bonus. These are referred to as Circumstance Bonuses or Penalties. More often than not, however, rather than numerically modifying your d20 Test, a given Test will instead be given Advantage or Disadvantage to represent the circumstances at hand. These two circumstances are discussed in more detail here.
The basic formula for a d20 Test looks like this:
1d20 + Relevant Ability Score Modifier (Positive or Negative) + Proficiency Bonus (if applicable) + Any Circumstance Bonuses or Penalties vs. Task Difficulty Class
When applying Advantage or Disadvantage to the roll, the formula looks like this:
2d20 (Keep the Higher or lower die, depending) + Relevant Ability Score Modifier (Positive or Negative) + Proficiency Bonus (if applicable) + Any Circumstance Bonuses or Penalties vs. Task Difficulty Class
Failing Forwards
Where possible, use failed d20 Tests to present interesting outcomes and to keep the adventure moving forward. If a thief attempts to pick a lock using thieves’ tools, rolls poorly, and fails to meet the DC, the DM has a choice: “You can’t pick the lock,” and stalled progress, or limited success and a setback.
For example, the DM might instead say, “if you continue you’ll pick the lock, but it will take several minutes. There are guards patrolling this building, do you want to risk it? What do you want to do?”
A Passive Test is a special kind of d20 Test that doesn’t involve any die rolls, instead representing any of the following circumstances:
To determine a character’s total for a Passive Test, add 10 + all the modifiers that normally apply to the test. If the character has Advantage on the check, add 5 and if the character has Disadvantage, subtract 5.
The most common use of a passive test is a passive Wisdom (Perception) check. When a character first experiences a new scene or location, the DM describes what they sense based on their perceptiveness. A highly perceptive character might automatically detect dangers a less perceptive character wouldn’t notice, such as hidden opponents or traps.
Sometimes one creature’s efforts are directly opposed by another’s. This happens when two or more creatures are attempting the same thing but only one can succeed (trying to snatch a fallen magic ring from the floor) or when a creature’s actions are trying to prevent another from accomplishing a goal (such as when an adventurer is holding shut a trapdoor while a monster is trying to force it open). In these situations the outcome is determined by a contested d20 Test—a contest.
Participants in the Contest make Ability Checks appropriate to their efforts and use an ability score chosen by the DM. They apply bonuses and penalties, but instead of comparing the total to a DC they compare the totals of their tests. The participant with the higher result wins the Contest, either succeeding at their action, or preventing the other from succeeding.
If the Contest has a tied result the situation remains the same as it was before the Contest—neither creature grabs the ring and the adventurer keeps the door closed. Alternatively, the participant with the higher relevant Ability Score modifier might succeed, but with a setback determined by the DM.
When you roll a 20 on a d20 Test—including Ability Checks, Attack Rolls, and Saving Throws—it is a Critical Success, while rolling a 1 on any the aforementioned tests is a Fumble. Below are the ways in which this rule is applied to each of the three core types of d20 Tests.