Natural 20’s on Skill Checks

Rolling a Natural 20’s on Skill checks has been a subject of debate for years. Some hold onto a house rules that rolling a Nat 20 is always some kind of success, even if a character’s stats are too low to succeed even with a 20. Of course, rolling a Natural 20 in combat is a critical success, always hitting its mark, but with skills this is a different story. In reality, what is determined on your skill checks is based on your Game Master, and your group. 

I’m not here to tell your group how to have fun, that’s all up to you! To me, as long as you’re having fun, then you’re playing it right! But that’s not where the discussion ends. First, I’m going to outline some of the arguments for each side, then I’m going to let you in on a secret.

A house-rule that can blow this argument wide open.

The Lines

Firstly, let’s lay some groundwork on skill checks. If a skill check is trivial and their request is within the realm of reason, then I recommend letting it happen. Maybe give it some extra narrative flair! If the barbarian is trying to break down a wooden door and rolls a Nat 20, have it shatter to splinters, anything to up the “cool factor”.

Alternatively, say a player declares to drink an entire lake in one go. Obviously, rolling a Nat 20 in this case would still result in a failure because the task is completely unreasonable. However, in a world of fantasy and magic, your players may not know what they are asking is impossible. In these cases tell them straight out, and don’t give them the chance to roll. Any time you let a player roll, they should have a chance at success.

The Tweet referenced

Clarified by Jeremy Crawford (Lead Rules Developer and Managing Editor for 5e), rolling a Natural 20 on skill checks does not guarantee success. For example, if there’s a DC 30 to determine the motivations of the Big Bad, then it’s a DC 30, and a Nat 20 does not guarantee a thing. However, from the player’s standpoint, if the 20 + their relative modifiers are not enough to succeed, they can feel cheated, because this is their best possible outcome. Asking a player to roll in itself implies that they have some chance of succeeding, rolling a Natural 20 and still failing is frustrating at best. You asked them to roll when there was no possible chance of success, which in the end makes everyone feel bad.

Exploding 20’s

Honestly, this rule does make sense. With a d20, that would mean there is a 5% chance to get a 20 for each roll. That would mean that you have a 5% chance to succeed on anything! But what can be done about this? The GM shouldn’t have to ask everyone their stats before asking them to roll, that would be just ridiculous! I feel like it’s time for a house rule, Exploding 20’s! 

Exploding 20’s
On a Skill Check, any time a Player rolls a Natural 20 they may choose to keep the result of 20 or to chance having the 20 Explode. When exploding, the player will roll their d20 again, subtract 10, then add it to their previous roll. If the player rolls a subsequent 20 within the same roll, they may keep electing to have it explode.

This house rule provides an interesting opportunity for Natural 20’s on skill checks, one where players can choose to “press their luck” for a higher score. On the exploded d20, rolling a 1-9 would actually cause their overall score to decrease. (Unless you just decide to ignore everything below 10. It’s your house rule!) But, rolling an 11 or higher would net them a roll over 20 before modifiers. 

Oh Geez, Some Math.

This also mitigates the “5% chance to do anything” problem as well. Increasing levels of difficulty have a less percent chance of success. Let’s use the DC 30 example from above, and give the player a +5 modifier to their roll. This would mean that if player managed to roll a Nat 20 on their first roll, then choose to explode the die, they would still need a 15 or higher on the second die meet their DC. 

(20 roll) + (15 [-10] exploding roll) + (5 modifiers) = 30

OK, now this is just feels like a math lesson, but it has to be done! Overall, when the player decides to roll against a DC 30 with a +5 Modifier, they would have to roll a Nat 20 (with a 1/20 chance), then a 15 or more (with a 6/20 chance) to succeed. This translates to a 3/200 chance of success, or a 1.5%. Much better than the 5% from before!

Unreasonable DCs

This opens the doorway to create some truly unique scenarios. Instead of having things be outright impossible due to level restrictions, they merely become increasingly improbable. This leads to an interesting situation, one where players still have a chance to succeed in a way they otherwise would not be able to, based on incredibly unlikely odds.

Nat 20 Ride Check as a Meme
What DC would you set to do this? via

Let’s say your players want to punch through a mountain pass, but are clearly not deities, so this task would be impossible. However, instead of leaving it to be impossible, consider giving it a higher DC. Let’s say its a DC 40, and they have a +10 in relevant modifiers. In this case they would need to roll two Nat 20’s in a row to succeed. That’s a 1/400 chance (or 0.25%)! Getting this result will cause a chain reaction to a rock slide that has been building up for years, creating a passageway over the mountain.

(20 roll) +(20 [-10] exploding roll) + (10 modifiers) = 40

The Malechi Effect

And before you say it would never happen, allow me to introduce you to something I like to call the Malechi Effect. If there’s a chance for it to happen, it inevitably will at some point. Be it Fate, or the “Dice God, God of Dice” as Logan says, D20’s have a way of making important rolls critical (be it good or bad). A friend of mine that was in an RPG group with me once proved this point.

In one of our first campaigns playing Star Wars d20, Malechi and the rest of the group were facing off against a Trade Federation tank. And that’s when Malechi decided to shoot right down the barrel, trying to get the cannon to backfire. 

A picture of a Trade Federation Tank
Trade Federation Tank via

Of course, I laughed and said, “give it a shot” never in a million years thinking that he could roll high enough for me to consider it. At this point, I didn’t even create a DC! And that’s when I saw it. On that day, Lady Luck was in the party, at that table, as Malechi rolled a Nat 20, then another, then another, then…

In total he rolled 8 dice, meaning 7 of them were Nat 20s. That’s a 1/1.28 Billion. Yes, that’s Billion with a B. The odds of winning the jackpot on a powerball is only something like 300 million, 4 times more likely! Oh, and his last roll was an 18, just adding insult to injury! This is a result of 88 before modifiers!

Needless to say, he destroyed the tank before combat even started officially, and the session was ended about an hour early (but in a good way). What thoughts do you have on Natural 20’s on skill checks, or house rules? Let us know in the comments below!