A natural 20 (or "nat 20") is when the twenty-sided die lands showing a 20 before you add any bonuses. A natural 1 ("nat 1") is the opposite: the die shows a 1. On an attack roll, a nat 20 is a critical hit and a nat 1 is a critical miss, sometimes called a fumble. These two results are the most celebrated and most feared rolls in tabletop RPGs, and they have become a shorthand for "the dice did something dramatic."
This guide uses Dungeons & Dragons 5th edition (5e) as its reference, since it is the rule set most players mean when they say these words. Other systems vary, but the core idea travels well.
The word natural points to the raw number on the d20 itself, with nothing else factored in.
Most rolls in 5e are not just the die. You roll the d20, then add modifiers: your ability score bonus, your proficiency bonus, magic items, and so on. The total is what you compare against a target number.
"Natural" strips all of that away. A nat 20 means the die physically shows 20, even if your modifiers would have pushed the total far higher anyway. A nat 1 means the die shows 1, no matter how big your bonuses are. The distinction matters because some rules trigger on the raw die, not the final total.
A critical hit is the moment players live for.
In 5e, when you roll a natural 20 on an attack roll, two things happen. First, the attack automatically hits, regardless of the target's Armor Class. Second, you get to roll the attack's damage dice twice and add them together, then apply your usual modifier once.
So if your sword normally deals 1d8 + 3, a critical hit means you roll 2d8 and then add 3. Extra dice from features like a rogue's Sneak Attack are also doubled on a crit, which is why some builds hit terrifyingly hard when the 20 comes up.
The thrill is real. A crit can drop a boss a round early, turn a desperate fight, or simply produce a number nobody at the table will forget.
The mirror image is the critical fail.
In 5e, rolling a natural 1 on an attack roll is an automatic miss, no matter how high your modifiers are or how low the target's defenses look. That is the only thing a nat 1 officially does on an attack.
Here is the part many players get wrong. By the rules as written (RAW), ability checks and skill checks do not automatically succeed on a 20 or automatically fail on a 1. A natural 20 on a Persuasion check or a lockpicking attempt is just a 20 plus your modifier; if that total does not meet the difficulty, you still fail. The "nat 20 always works, nat 1 always flops" idea is a house rule — a popular one, but not the official rule.
The same goes for saving throws in the core rules: only the 2024 revision made nat 20s and nat 1s matter on saves, so check which version your table uses.
Many groups spice things up with crit and fumble tables — charts you roll on when you score a natural 20 or natural 1.
A fumble table might make you drop your weapon, hit an ally, or trip. A crit table might let you sever a limb or hit a weak point. They are genuinely fun and produce great stories.
But there is a fairness catch worth knowing:
If your table uses them, consider scaling the consequences so the warriors are not penalized for doing their job.
Crits and fumbles endure because they are collaborative theater.
A natural 20 gives the whole table permission to cheer, and a smart Game Master leans into it — describing a clean strike or a clutch escape. A natural 1 invites a groan and a laugh, and often a story that gets retold for years.
These rolls create shared memory. They turn a string of numbers into a moment everyone witnessed together, which is a big part of why people keep coming back to the table.
A few neighbors worth knowing:
When you are rolling in Mini Kraken, the dice roller flags natural 20s and natural 1s automatically, so you will never miss the moment a crit lands.