Making Skill Checks More PBTA

Image (cc) oxpal
One thing I loved when reading Dungeon World was how all the moves fall into the same basic pattern:
  • 10+ (on 2d6 plus modifiers) means clean success
  • 7-9 means success, but with a cost or limitation
  • 6 or less means failure and the DM moves the story along
It's an easy change from pass/fail and it runs right through all "Powered by the Apocalypse" games.  Note how there's no DC. I like this. So often my players roll skill checks and announce the result before I decide the DC that I end up just eyeballing it - so why not get rid of it? This is all about stakes and not about difficulty.

So for my beloved Stars Without Number it's an easy enough change for me to want to start using it, I guess it is for any other 2d6 system, but can we apply it to D&D?  Mathematically (according to AnyDice and some probability calculations) this should map to 18+, 9-17, and 8 or less which is actually not too clunky!

However, 2d6 and 1d20 give totally different distribution shapes, so any modifiers are going to swing things differently, right?  Actually, it looks like things still hold roughly similarly if each +1 on 2d6 is equivalent to +3 on a d20.  Given that 5e maxes out at +10 on a roll could that actually work?

Given how nicely 18 and 9 are related, could we make it work with DCs too as long as the "success, but" number is half the "success" number?  Your thoughts are very welcome!


  1. I'm trying to figure this out myself. I was actually thinking about ditching the d20 and having my players use 2d6 for non-combat rolls, and figuring out how to map skills to PbtA appropriate modifiers. I don't have a good idea yet but am on the hunt for others who may have done similar things.

  2. Stars Without Number / Worlds Without Number uses d20 for combat but 2d6 for skill checks.


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