How Many PCs Can Try a Skill Check?

A character tries to roll a skill check in D&D or another RPG. The rest of the players want to roll at the same time. Should we allow that? Let’s examine the math!

First, Lessons From DMAP

A quick note! I’ve been examining various aspects of how to run great games through the lens of the new Dungeon Masters D&D official actual play. It’s been fun to see the Do’s and Don’ts of the series.

Episode 1: Character backstory, NPCs as your voice, the known surprise.

Episode 2: 2 Do’s and 2 Don’ts: Story before combat, player negotiation, agency loss, PC emotions.

In addition, this blog you are reading on skills is available as a video.

The Skill Dogpile

If you’ve DMed long enough, you have probably had the experience where you describe the scene and a PC asks if they can try something. “Can I make an arcana check to inspect the idol?” Suddenly, several other players pick up their D20 and start to roll too!

Should everyone be able to roll? Should they be able to assist? Should they be able to boost the roll with a class feature such as Bardic Inspiration or a spell like Guidance?

I should pause and say this isn’t just for D&D. Many RPGs see this kind of behavior. I’ll use D&D as an example and speak to a few other RPGs, but it impacts many RPGs.

Good Player Practices

Players, we should adopt some good practices. First, respect the player that came up with the idea. Imagine a big spotlight that suddenly turned on and shone on the player suggesting that Arcana check. If we start rolling, we are robbing them of the moment. Think of them as having the momentum or priority. It’s currently their scene and we want to respect that.

Now, maybe the barbarian is the one that had the idea and we are playing the wizard. Or maybe our backstory is creating arcane idols. We may feel it makes a lot of sense to cut in. We can still do so respectfully: “In character, my wizard would be very interested in what you are doing, even to help you with that check. Out of character, how good is your character at Arcana?” This respects their idea, but gives them the possibility of tagging you in or requesting help.

This becomes more important if it’s a high-stakes roll. Maybe we learned earlier that the idol will set off a horrid trap. We can mention that. And if we are playing the barbarian, we want to respect the other party members and not just make a high-stakes roll when we aren’t good at it if that will hurt the fun at the table. Mutual respect will create the best play experiences over time.

Don’t Just Roll

Similarly, a good practice is to start with the fiction. Don’t walk into the room where the crime took place and say, “I roll Perception: 27. What’s here?” Such play puts the DM in a tough situation by making the assumption that whatever is in this room is solved by one roll, suggests you don’t actually care about gameplay, and cuts off other players from participating.

Instead, lead with the fiction. “I’m eager to solve the crime. I look to my team and carefully step into the room, slowly taking in the details.” Pause and look to the DM. You might further ask something like “I’m looking for anything out of place and anything that could be a murder weapon.” Then let the DM respond. They may add detail to the room, may ask for a roll, or may involve other players. Allowing for the natural back-and-forth between DM and all players will create a more rewarding experience over time.

When another player makes a roll, we shouldn’t just start rolling as well. Always ask, “Is it possible for more than one PC to make this check?” This makes sure to not intrude on the person already in the spotlight and lets the DM respond. And here’s why the answer should probably be no…

The Problem with Multiple Rolls

Modern RPGs take math very seriously. Designers ponder the expected interaction between characters and the game world. The difficulty of a check is set in tandem with the character’s expected range of capabilities, the dice we use for resolution, and various other parts of the game. This is true in Alien, Night’s Black Agents, D&D, Daggerheart, Draw Steel, etc. The probability and dice can change, but it’s still something balanced by the game.

When a challenge is based on a roll, and failure carries no consequence, then multiple rolls will trivialize the challenge.

Interestingly, both Daggerheart and Draw Steel minimize this problem because failure in those games can make things worse. In Draw Steel, failing at even an easy check results in a complication. Tests can be hard, so multiple rolls provide just one success but could result in multiple complications. Failing in Daggerheart gives the GM Fear they can spend to make your life harder or introduce a complication.

In D&D, there is no such impact. Here, it helps to understand the math and why we should change our behavior.

Understanding the Math

Let’s say we have a typical tier 1 D&D character. A character with an applicable skill and where that skill is attached to their primary ability probably has a +5 to their roll. (No expertise, which would add +2.)

A medium difficulty is DC 15. This is expected to have a fair chance of failure! That may be surprising, but it is how the game is set up. (An easy difficulty has a DC of 10.)

1d20+5 has a 55% chance to attain a result of 15 or higher. With Expertise, 65%.

How about the spell Guidance, which adds a 1d4 to the result? You go from a 55% chance to a 67.5% chance. So, a 12.5% boost. That’s significant! If the DC is 20, with guidance is a 42.5% chance, without it 30%.

How do multiple rolls impact the probability? Let’s assume we have 5 party members, and on average have a +2 bonus to their roll, and we let everyone roll that DC 15 check.

Rolling 5 d20s, the chance that someone rolls a 13 or higher is 92.2% So, success goes from a bit over half the time to being extremely likely! Even rolling a 15, where we assume the characters have no bonus to the roll, is an 83.19% chance! So, as you can see, multiple rolls will vastly change the math.

While we are at it, what about the Help Action?

Multiple rolls is very different from advantage, where the Help action or some other factor providing advantage is useful, but not completely game breaking. Let’s go back to our character with a +5 bonus. Rolling a single die, they have that 55% chance of achieving a 15 or higher.

With advantage, they roll 2 d20s, and that’s a 79.75% chance of getting a 15 or higher.

With guidance and advantage, that’s an 89.13% chance of getting a 15 or higher, so even better than the multiple rolls with a +2 bonus (though in reality, some probably may have Guidance and some may have a higher or lower bonus). Still, it’s similarly breaking the expected probability.

Have We Broken the Game?

Go back to the definition of the challenge. It’s a Medium difficulty. Does an 89% chance of success sound like medium? Nope, it’s really easy! So, we are breaking the game’s expectations.

Is that bad? Well, it depends. As we said in the last blog article, when we call for a check we usually want there to be stakes. We want there to be some drama, the possibility that failure could be interesting, or that something is being determined.

But, not always. If we like rolling to create engagement, and there are no or only minor consequences to the roll, then everyone rolling can be fun. “Give me a History check to see if anyone remembers rumors about this tavern.” Everyone rolls, we take the highest, and based on that improvise what they hear out of various possible ways to answer the question.

Multiple rolls might help the DM assess how well the players understand something. For example, how many players think the noble is trustworthy, or the degree to which they know that the forest is corrupted. It’s like a temperature test or survey of the characters.

When to Use Single Checks

Single checks should be the default when we want a challenge and stakes matter, because the math favors that. It is good for both players and GM to understand that this is how the game works. When it comes to challenges, the baseline is a single roll with the expectation of neither Guidance nor Advantage. Adding either Guidance or Advantage is a significant boost, but not nearly as big as both combined.

Ideally, we want players and DM to understand the expectation of good gameplay at a meta level – that single rolls and unaided rolls should happen often. At the fiction level, it can be harder. Sometimes it makes sense. Five people can’t crowd around the lockpick. We can make a reasonable argument that only one can. But, what about searching for tracks or trying to get a read on the possibly duplicitous NPC?

Here, we can lean on the gameplay. We can say, “Choose one person to take the lead on this effort.” The idea is, the game knows everyone is looking for tracks, but one person is the lead and their roll is what represents success or failure. Anyone could size up the NPC, but we are spotlighting one PC to represent this and determine success or failure.

When to Allow Help and Guidance

Help and Guidance are great in moderation, especially moments when there is no time pressure and everyone is grouped together and making decisions together. It works well for gameplay when we want a high chance at success or a reward for playing together.

One way we can gently suggest to players to be reasonable is to ask them to describe how they Help and to describe each time how they ask their deity to provide Guidance. Doing so lets them know this takes time and focus. And, we can tell players outright that Guidance, which takes an action, can’t be cast when it’s a split-second decision or if casting would be problematic (such as in front of an NPC you are trying to persuade). The range is also touch, potentially placing the caster in danger. But, mostly, “look, be reasonable. I don’t want to chance the DCs to all be harder. Use it sparingly, when it makes sense.”

Help similarly takes time to do and shouldn’t be done on every single role. Players: save it for scenes where working together makes sense, there is time to do so, and lean into the fiction to describe how you help. Consider sharing something about your backstory or otherwise roleplaying the moment when you help an ally.

When to Use Group Checks

A group check is a special check where every player tries the check and if half or more succeed, the entire group succeeds. This is perfect for scenes where the story is told not by the skill of one player, but by the collective action of the team shaping the result. Examples include searching a room, sneaking past the mansion ground guards, and successfully traveling through the wilderness. It works particularly well to capture events taking place over time, rather than all at once.

The mechanics and flavor of a group check are excellent for determining an overall state. For example, whether you find enough clues (and you can even give out those clues with each success), whether you travel across the desert well (and each check might be a unique challenge or a unique contribution to the travel). You can look to 4E skill challenges, Draw Steel Montages, and similar systems for deeper systems than a 5E group check.

Beyond the Roll

You can also consider systems like Gumshoe and Night’s Black Agents, where being proficient in investigative skills means you don’t roll at all. You automatically find the clue. These RPGs help us as DM shift the emphasis from whether we find the murder weapon. I mean, think about it. In most D&D scenarios, that’s actually the expectation. Given that, the actually important question is what the party does with the clues. Yes, you know the murder was done by a faction, and you also know that a rival faction would use that information to destabilize the nation. Now, what do you do? This helps us start to look at skills and tests in entirely different ways.