Odds of Rolling a Natural 20 (and with Advantage)

What are the odds of rolling a natural 20?

A "natural 20" means the d20 itself shows 20, before any bonuses are added. A fair d20 has twenty faces with equal chances, so each roll has a 1 in 20 chance of landing on 20. That's 5%.

The chance is the same on every roll. Dice have no memory, so missing a nat 20 for an entire session doesn't make the next one more likely. You can test that yourself with the d20 roller, which uses your browser's cryptographic random number generator.

What are the odds of a natural 20 with advantage?

With advantage you roll two d20s and keep the higher, so you get a natural 20 if either die shows 20. The easiest way to calculate it is to find the chance that neither die is a 20 and subtract that from 100%.

• Normal: 5%.
• Advantage (two dice): 1 − 0.95 × 0.95 = 9.75%.
• Elven Accuracy (three dice): 1 − 0.95³ = 14.26%.
• Disadvantage: both dice must be 20, so 0.05 × 0.05 = 0.25%, or 1 in 400.

Elven Accuracy is a feat from Xanathar's Guide to Everything. When you have advantage on certain attack rolls, it lets you reroll one of the dice, which in practice means rolling three d20s and keeping the highest. More on how advantage shifts every target number is in advantage and disadvantage in 5e.

What if you crit on a 19 or 18?

Some features widen your critical range, such as the Champion Fighter's Improved Critical (19–20) and later Superior Critical (18–20). The same formula applies:

What are the odds of getting at least one natural 20 in several rolls?

Over a fight or a session you make many d20 rolls, so the useful question is often "how likely am I to see at least one 20?" The answer is 1 minus the chance of missing every time: 1 − 0.95^N for N normal rolls.

• Coin-flip point: it takes 14 rolls to pass a 50% chance of seeing a natural 20 (51.23%). With advantage, 7 rolls is enough.
• Average wait: 20 rolls on average, but there is about a 13% (12.85%) chance of going 40 rolls in a row without one.
• No guarantee: even after 59 rolls there is still a 4.85% chance you haven't rolled one.

How often will you crit in a typical fight?

Characters with several attacks per turn see natural 20s much more often than the 5% per roll suggests. A few examples, using the at-least-one formula:

• One attack a turn for 4 rounds: 4 rolls, 18.55% chance of at least one natural 20.
• Two attacks a turn for 4 rounds: 8 rolls, 33.66%.
• Three attacks a turn for 4 rounds: 12 rolls, 45.96%.
• Two attacks a turn with advantage, 4 rounds: 16 dice in total, 55.99%.

That's why Fighters with Extra Attack and characters who can reliably get advantage, like a Barbarian using Reckless Attack, crit noticeably more often over a campaign. Bonuses to hit don't change the chance of a natural 20 at all; only more dice or a wider crit range do.

What does a natural 20 do in D&D 5e?

What a natural 20 does depends on the type of roll. The 2014 and 2024 Player's Handbooks agree on the basics.

Attack rolls

A natural 20 on an attack roll always hits, no matter the target's Armor Class or your modifiers, and it is a critical hit. On a critical hit you roll the attack's damage dice twice and add your modifier once. Read more in critical hits in 5e.

Ability checks and saving throws

In the core rules a natural 20 is not an automatic success on an ability check or saving throw. You add your modifier and compare the total to the DC as usual, so a character with a −1 who rolls a 20 against a DC 25 still fails. The 2024 rules call attacks, checks and saves "D20 Tests", but the automatic hit on a 20 is still written for attack rolls only.

Many tables use a house rule that a 20 on a check is a great success, or at least the best possible outcome. That's a table decision, not a rule, so ask your DM.

Death saving throws

A natural 20 on a death saving throw is special in both editions: you regain 1 hit point and wake up. A natural 1 counts as two failures.

What about a natural 1?

A natural 1 has the same 5% chance as a natural 20. On an attack roll it always misses, regardless of bonuses. On ability checks and saving throws the core rules give it no special effect beyond being the lowest roll, though many groups treat it as a fumble. With advantage the chance of a natural 1 drops to 0.25%, and with disadvantage it rises to 9.75%.

Is rolling a d20 online as random as a real die?

A good digital roller gives each face exactly a 5% chance. Physical dice can be slightly off because of manufacturing flaws, air bubbles or rounded edges, though most are close enough that you'd never notice at the table. Either way, every roll is independent, and the 5% chance is the same on every throw. For more about the die itself, see what is a d20.

FAQ

What are the odds of rolling a natural 20?

5%, or 1 in 20, on any single d20 roll. Every face of a fair d20 is equally likely.

What are the odds of rolling two natural 20s in a row?

1 in 400, or 0.25%. That is 5% times 5%, the same as rolling a natural 20 with disadvantage.

Does a natural 20 automatically succeed on a skill check in 5e?

Not in the core rules. The automatic success on a 20 applies to attack rolls. For ability checks and saving throws you still compare your total to the DC, though many tables use a house rule that a 20 always succeeds.

How many rolls does it take to get a natural 20?

On average 20 rolls, but it varies a lot. You have about a 51% chance of at least one natural 20 within 14 rolls and about a 64% chance within 20 rolls.

Does a natural 20 on a death saving throw do anything?

Yes. In both the 2014 and 2024 rules, a 20 on a death saving throw means you regain 1 hit point and become conscious.

Related

• Roll a d20
• Advantage and Disadvantage in 5e: How It Changes Your Odds
• Critical Hits in 5e: How Crit Damage Works
• What Is a d20? Odds, Uses and History of the 20-Sided Die