Ability Checks and DCs, How Hard Is Hard
A locked door, a lying merchant, a cliff in the rain. None of them is a fight, and every one of them can go wrong. That is what the ability check is for.
What an ability check is
SRD 5.2.1 puts it plainly:
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.
It also says when to roll one, and the second half matters more than the first:
When the outcome is uncertain and narratively interesting, the dice determine the result.
If the task cannot fail, or failing changes nothing, nobody rolls. Opening an unlocked door is not a check. Opening it quietly, with a guard asleep on the other side, is.
Which ability
A check takes its name from the ability modifier it uses: a Strength check, a Wisdom check. The SRD's Ability Check Examples table gives one job to each:
| 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 |
Most checks also name a skill: Strength (Athletics), Charisma (Persuasion). There are eighteen skills, and each sits under the ability it "most often applies to". Stealth sits under Dexterity, Insight under Wisdom, Arcana under Intelligence.
The roll
Every check is a D20 Test, and the steps never change:
- Roll 1d20 (two and keep one, with Advantage or Disadvantage).
- Add the ability modifier.
- Add your Proficiency Bonus if a skill or tool you are trained in applies.
- Compare the total with the DC. Equal to or higher succeeds.
Step 3 is the one people get wrong. The SRD:
Without proficiency in a skill, a creature can still make ability checks involving that skill but doesn't add its Proficiency Bonus.
So anyone can try to climb the cliff. The trained climber just adds +2 at level 1, rising to +6 by level 17.
How hard is hard: the DC
The GM sets the number. The SRD gives the scale:
| Task difficulty | DC |
|---|---|
| Very easy | 5 |
| Easy | 10 |
| Medium | 15 |
| Hard | 20 |
| Very hard | 25 |
| Nearly impossible | 30 |
What those words mean at the table depends on your bonus. Take two level 1 characters. One has a +3 ability modifier and the skill: +5 total. The other has +0 and no skill.
| DC | +5 (trained, 16 in the ability) | +0 (untrained, 10 in the ability) |
|---|---|---|
| 5 | 100% | 80% |
| 10 | 80% | 55% |
| 15 | 55% | 30% |
| 20 | 30% | 5% |
| 25 | 5% | 0% |
| 30 | 0% | 0% |
Each line is plain counting: the trained character beats DC 15 on a 10 or higher, which is 11 faces of 20. Two things fall out of the table.
Medium is a coin flip for the specialist. DC 15 is not a routine task; it is the point where your best skill fails almost half the time.
Nearly impossible means impossible at level 1. A d20 plus 5 tops out at 25. DC 30 waits for higher levels, magic, or a different plan.
A natural 20 is not an automatic success
At most tables someone cheers a 20 on a check. The SRD's "Rolling 20 or 1" rule applies to attack rolls only: a natural 20 hits "regardless of any modifiers or the target's AC". For an ability check, a 20 is just 20 plus your bonus. Against DC 30 at +5, it still fails. Some tables play it otherwise; that is a house rule, and worth agreeing on before the session.
Getting the odds up
Help. The Help action is the cheapest bonus in the game:
Choose one of your skill or tool proficiencies and one ally who is near enough for you to assist verbally or physically when they make an ability check. That ally has Advantage on the next ability check they make with the chosen skill or tool.
Advantage moves our trained character's DC 15 from 55% to 79.75%: the check fails only if both dice miss, 0.45 × 0.45 = 20.25%.
Skill and tool together. Proficiency with a tool adds your Proficiency Bonus to a check that uses it. Proficiency in the skill as well grants Advantage on top. The SRD: "you can benefit from both skill proficiency and tool proficiency on the same ability check."
Watch for Disadvantage. Frightened gives Disadvantage on ability checks while the source of fear is in sight, and so does trying to Influence a Hostile creature. Both sink a 55% check to 30.25%.
Passive checks
Some checks nobody rolls. Passive Perception, for one, is a fixed score the GM compares in secret:
Passive Perception = 10 + Wisdom (Perception) check modifier
Our +5 character has a Passive Perception of 15, so they notice anything hidden at DC 15 or lower without lifting a die. It works as a check that always rolls 10.
At the table
When a player says what their character does, the GM asks three questions: can it fail, does failing matter, and how hard is it? Two yeses and a number from the table above make a check. Name the ability and the skill, say the DC out loud if your table likes it, and let the die decide.
The Book of Dice covers the d20 in Part I, The Object, and every way of rolling it in Part III.
This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License.
