Why Are skill DCs 10+mod instead of 11+mod?


Rules Discussion


Pathfinder Adventure, Adventure Path, Lost Omens, Rulebook Subscriber

Using 10+modifier for opposed skill checks results in a bias in favor of the rolling party. Shouldn't it be 11 + modifier?

Example: a PC hides from a monster. The PC's stealth is +0, and monster's perception is +0. Even-Steven, right? No, the Perception DC is 10+0 = 10, meaning the PC successfully hides on a 10-20 roll (11 permutations, 55%), and is spotted on a 1-9 (9 permutations, 45%).

The same is true with opposed skills like deception and perception. The CRB tells a lying PC to roll Deception vs Perception DC, but if the PC is Sensing Motive they roll Perception vs Deception DC. If all modifiers are +0 again the PC has a 55% chance of success, so long as they are the one rolling. It's like the PC has a secret little boost during these NPC interactions.

If the rule was 11 + mod then equal modifiers would produce even odds. Wouldn't this have been a better way?


Pathfinder Maps, Pathfinder Accessories, Pawns, Starfinder Society Subscriber; Pathfinder Roleplaying Game Superscriber

See previous discussion of this issue
Why 10+ and not 11+


Pathfinder Adventure, Adventure Path, Lost Omens, Rulebook Subscriber
CrystalSeas wrote:

See previous discussion of this issue

Why 10+ and not 11+

That thread is about critical success/failure thresholds, which isn't what I'm talking about above.


Pathfinder Maps, Pathfinder Accessories, Pawns, Starfinder Society Subscriber; Pathfinder Roleplaying Game Superscriber
Cyprion wrote:
That thread is about critical success/failure thresholds, which isn't what I'm talking about above.

Both discussions are about the reasons for +10 and not +11 on skill rolls. That thread starts out talking about critical results, but quickly moves into the more general case of *all* results.

Scan through the thread until you reach the answers to your question.


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Cyprion wrote:

Using 10+modifier for opposed skill checks results in a bias in favor of the rolling party. Shouldn't it be 11 + modifier?

Example: a PC hides from a monster. The PC's stealth is +0, and monster's perception is +0. Even-Steven, right? No, the Perception DC is 10+0 = 10, meaning the PC successfully hides on a 10-20 roll (11 permutations, 55%), and is spotted on a 1-9 (9 permutations, 45%).

The same is true with opposed skills like deception and perception. The CRB tells a lying PC to roll Deception vs Perception DC, but if the PC is Sensing Motive they roll Perception vs Deception DC. If all modifiers are +0 again the PC has a 55% chance of success, so long as they are the one rolling. It's like the PC has a secret little boost during these NPC interactions.

If the rule was 11 + mod then equal modifiers would produce even odds. Wouldn't this have been a better way?

Because even mods aren't actually good for the game. Having slightly offset mods means that the advantage is always slightly in favour of the person taking action.

Basically, it emphasizes doing things to gain advantage instead of just sitting around.


Doesn't everyone benefit from that as often as they are penalized by it anyway?


Pathfinder Lost Omens, Rulebook Subscriber

To take the converse example, if the monster actively searches they get to roll against the stealth dc, reinforcing Cyoinis point that the party spending resources (an action in this case) gets the advantage.


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Because adding ten to a number is easier.

Sovereign Court

Matthew Downie wrote:
Because adding ten to a number is easier.

Yeah I thought that was obvious.

The Exchange

The vast majority of the game is designed for ease of play. Telling a person to add 10 or subtract 10 can be done with almost no thought. Bear in mind that the margin of success and failure does not have to be identical since the rules only talk about the process being similar. (the game is NOT an exact simulation that requires precisely balanced and accurate processes)

Alternate approaches add unnecessary layers. For example, I do not want to be told that the actual DC of a task is never a whole number so you can never just succeed (14.5 instead of 15, thus a 14 is F-1, 15 is S+1). I also do not want to be told that you need to add 11 in one direction and 10 in another


Cyouni wrote:


Because even mods aren't actually good for the game. Having slightly offset mods means that the advantage is always slightly in favour of the person taking action.

Basically, it emphasizes doing things to gain advantage instead of just sitting around.

While I don't disagree with your general premise, this isn't always true. Save-granting effects are an obvious big one. If I cast a spell that targets a save or perform a strike that comes with a debuff, I'm the one spending resources and at a disadvantage to the roll.


Pathfinder Card Game Subscriber; Pathfinder Roleplaying Game Superscriber
Laran wrote:

The vast majority of the game is designed for ease of play. Telling a person to add 10 or subtract 10 can be done with almost no thought. Bear in mind that the margin of success and failure does not have to be identical since the rules only talk about the process being similar. (the game is NOT an exact simulation that requires precisely balanced and accurate processes)

Alternate approaches add unnecessary layers. For example, I do not want to be told that the actual DC of a task is never a whole number so you can never just succeed (14.5 instead of 15, thus a 14 is F-1, 15 is S+1). I also do not want to be told that you need to add 11 in one direction and 10 in another

Or that the DC is 1.5 times the creature's level, plus a number. Looking at you, Starfinder.

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