Does rolling a NAT 20 always succeed?
A natural 20, or nat 20, is one of the most exciting moments in Dungeons & Dragons. As a DM, nothing gets players jumping out of their seats faster than the shout of “NAT 20!” when that critical hit is rolled.
But across many tables, a myth has arisen that a natural 20 represents automatic success on any d20 roll. This leads to improbable outcomes like bardic seductions of ancient dragons. So does a nat 20 really mean you can‘t fail? Let‘s analyze the math and rules behind critical hits to find out.
Nat 20s only auto-hit and crit on attack rolls
The D&D 5th edition Player‘s Handbook is clear that natural 20s have special meaning only in one specific case:
“If the d20 roll for an attack is a 20, the attack hits regardless of any modifiers or the target‘s AC. This is called a critical hit”
So RAW, an automatic hit and critical occur when you roll a 20 on an attack roll only. Despite many groups using homebrew rules, a natural 20 does not auto-succeed on saving throws or ability checks like Stealth, Persuasion, Perception, etc.
Jeremy Crawford, D&D‘s principal rules designer, confirmed this on Twitter:
“A natural 20 doesn‘t bypass limitations on ability checks. If a task is impossible, rolling a 20 doesn‘t make it possible.”
So by the books, a nat 20 is just another number unless it‘s for an attack roll.
The elusive nat 20 – Just a 5% chance
When rolling a d20, the odds of each result are equal. Each number has a 5% (1 in 20) chance of coming up.
What are the odds of getting multiple nat 20s? The probabilities diminish rapidly:
- Chance of two nat 20s in a row: 0.25%
- Three consecutive nat 20s: 0.0125%
- Four nat 20s in a row: 0.000625%
The chance of multiple nat 20s decreases exponentially based on independent probability calculations:
| Nat 20s in a row | Probability |
|---|---|
| 1 | 5% |
| 2 | 0.25% |
| 3 | 0.0125% |
| 4 | 0.000625% |
| 5 | 0.00003125% |
As shown in the table above, getting two nat 20s in a single D&D session is unlikely, let alone a mythical triple 20! Of course, advantage can greatly improve these odds…
Modifiers still impact nat 20 attack rolls
On attack rolls, rolling a natural 20 means an automatic hit and critical, even if the target‘s AC is higher than 20. But your attack modifiers are still added to the total roll.
This means even against an ancient red dragon with 25 AC, a level 20 fighter with a +15 attack bonus would still crit:
Nat 20 + 15 modifier = 35 total, hitting AC 25.
However, for very high DCs outside of combat, even a nat 20 can fail if your bonuses aren‘t high enough. Consider this Epic Level skill check:
| Roll | Modifier | Total | Success? |
|---|---|---|---|
| Nat 20 | +0 | 20 | No |
| Nat 20 | +5 | 25 | No |
| Nat 20 | +10 | 30 | Yes |
As shown above, a +0 or +5 bonus isn‘t enough for success on DC 30, but a +10 passes this near-impossible check even with a low nat 20 roll.
Nat 1s are not auto-fail outside attacks
The flip side to the natural 20 is the humble natural 1. Again, the rules are specific that rolling a 1 applies special meaning only to attack rolls:
“If the d20 roll for an attack is a 1, the attack misses regardless of any modifiers or the target‘s AC.”
Just like nat 20s, rolling a 1 is not an automatic failure on saving throws, ability checks, or skill checks. With high enough bonuses, a 1 can still pass!
For example, a Rogue with +11 to their Stealth check could still succeed on DC 15 with a natural 1:
Nat 1 + 11 bonus = 12 total, beating the DC 15 required.
Advantage and Disadvantage change the math
Having advantage or disadvantage on a d20 roll also alters the chance of scoring a critical hit or fumble.
With advantage, your chance of a minimum nat 20 jumps to 9.75%. The probabilities approximately double:
| D20 Rolls | Nat 20 Odds |
|---|---|
| 1 roll | 5% |
| Disadvantage | 0.25% |
| Advantage | 9.75% |
This makes features like a Barbarian‘s Reckless Attack incredibly powerful. You are much more likely to crit and devastatingly strike your foes.
By contrast, disadvantage makes nat 20s rare at 0.25%. So imposing disadvantage is an effective tactic to reduce the chance of enemy critical hits.
Critical Hits and Fumbles – expanding nat 20s/1s
Beyond the core rules, some DMs implement house rules that expand what nat 20s and 1s mean beyond just attack rolls:
- Critical Hits – Maximize all damage dice and add powerful additional effects on a nat 20.
- Critical Fumbles – Impose penalties, damage yourself, or other bad effects for rolling a 1.
However, these popular homerules do slow down play. As a DM, carefully consider if you want nat 20s/1s to have expanded consequences in your game.
The Psychology and Excitement of Automatic Success/Failure
Why are nat 20/1 house rules so common despite their issues? Because as players, we love the excitement and drama they generate!
Rolling a 20 feels like you "beat the system" and can accomplish anything, even for impossible tasks. Itscratchs a psychological itch. We abhor auto-failing on a 1.
These highs and lows create great stories – but come at the cost of bounded accuracy and verisimilitude. As much as we might laugh at seducing dragons, does it make sense in a fantasy world?
There are good arguments on both sides. As a DM, you must decide what is right for your table and strikes the desired balance.
The Evolution of Nat 20 Rules Across Editions
How have critical hit and fumble rules changed over time in D&D‘s different editions?
- AD&D 1e – No specific nat 20 or 1 rules. Critical hits determined by tables and charts.
- D&D 3.5e – Nat 20 = automatic hit, double damage. Nat 1 = automatic miss.
- D&D 4e – Nat 20 = max dmg + effects. Nat 1 = no effects.
- D&D 5e – Nat 20/1 apply only to attack rolls.
There has been a steady progression toward the current 5e rules. Interestingly, nat 20s granted extra effects in both 3.5 and 4e! So 5e devs deliberately scaled back to just double damage.
Other d20 systems like Pathfinder 2e continue to use expanded nat 20/1 rules. But 5e has trended toward simplicity.
Nat 20 Homebrew Rules in Popular Livestreams
How do popular D&D livestream shows like Critical Role handle nat 20s and 1s in their home games?
Critical Role uses a homebrew rule that a nat 20 on a skill check is a minimum of 25. This maintains bounded accuracy while still giving high rolls more impact.
For fumbles, Nat 1s have no special effects in Critical Role. Matt Mercer discussed why on Twitter:
"I don‘t do fumbles. Generally, they just serve to add more punishment to martial classes over spellcasters."
Critical Role‘s rules aim to enhance nat 20s while avoiding the problems of full auto-success or critical fumbles. Their homebrew strikes a smart compromise.
Guidance for DMs on Setting DCs and Bending Rules
As DM, when setting DCs, remember that impossible remains impossible even for nat 20s!
For DCs above 30, don’t be afraid to tell players success is unattainable. But also know when to ignore rules for dramatic moments that are just too cool.
My advice is to stick to RAW for nat 20s, but occasionally bend rulings on the fly when players do something creative and everyone is having fun. Just be cautious not to do this too often or it loses its impact.
Critical hits should remain special and epic heroic moments. But the rules are there for a reason – make sure you’re maintaining proper challenge and realism.
The Takeaway: Nat 20s aren‘t silver bullets
Despite house rules across many tables, RAW in 5e a natural 20 only guarantees success on attack rolls – not ability checks or saving throws.
Nat 20s are meant to be special moments, not silver bullets that allow anything to succeed. Be wary of devaluing obstacles and challenges too much.
But listen to your players and use your best judgement. The point of D&D is to have fun! Just carefully consider balance and bounded accuracy before implementing any major house rules.
Understanding how modifiers interact with DCs, and the rarity of rolling nat 20s, allows you to make sound rulings. Getting a natural 20 should feel like a triumphant moment – but not one that breaks the fabric of reality.