Advantage and Disadvantage in PBTA games

@BrianAshford Can you experiment with the cut off levels and number of dice to roughly equal pbta 2d6+x?

That is: To have roughly the same probabilities on Fail / Complication / Success as AW when mapping B[Nd6] to 2d6+K, what cutoff levels of fail/complication are required and what is the closest mapping from N to K?

Does that make sense? Am I asking a hard question?

1 Like



This one looks good!



I’ve thought a lot about advantage mechanics (my games core mechanic is stacking advantage!) and I feel like the main issue with PBTA in this regard is that there isn’t actual scaling when it comes to producing results from effects - it requires stronger moves to reflect the nature of high rolling.

I think the way I’d introduce this is to create advantage and disadvantage tables for moves - you’ll probably get better tuning out of how you want the system to function.

1 Like



I know this might feel a little off topic, but I think it would be worth mentioning here as another way of handling stackable (dis)advantage in PbtA.

The BitD style of rolling reminds me quite a lot of how FU RPG works.

My main issue with stacking advantage is how quickly we get to Full Success territory (or Yes, and… in FU). Again, this will depend on the style and feel of your game, maybe you are shooting for players not having any complications a lot of the time.

It seems that playing with Fail/Complication/Success target values remedies this a bit, but if you want more granularity in a stacking advantage, Earthdawn: Age of Legend (a more indie approach to the world of Earthdawn, based on FU RPG) does it in an interesting way.

Instead of advantage/disadvantage giving you an extra d6, it gives a Fudge die. If you have advantages and disadvantages at the same time, they cancel each other out (so 2 advantage and 1 disadvantage gives you total of 1 advantage).

Then you roll your d6 and amount of Fudge dice equal to your remaining advantage or disadvantage. With advantage, each + gives you +1 to what your rolled on the d6. With disadvantage, each - gives -1.

I haven’t played this version of FU / Earthdawn to give feedback myself, but according to the game text, each (dis)advantage changes the value of success/failure by roughly 10%.


Discussed this with @BrianAshford offline. Here is the suggestion to convert AW to having no addition, no subtract, and (almost) no negative numbers, using only d6s:

  • Take AW stats, add two. This is the number of dice.
  • 5’s and 6’s are successes.
  • a 10+ success requires two successes.

That works really well for 2d6 and higher, but has a problem with 1d6 or lower. These are fixed with:

  • When rolling just 1 dice, if it comes up 6 you can roll an additional die to try and get that second pass.
  • If you have to make a roll with less than 1 dice, roll as with 1 dice but 5s do not count as success for this roll.

These two fixes would make the conversion of -1 and -2 better than 95% accurate and still no maths or keeping the worse rolls.

I think I have this math right. It was done by Brian, so I may be somewhat off.


I guess it all depends on the type of game you are shooting for, but I would be ok with 1d6 not giving you an option for a full success.

Because the “exploding dice” working only when you are using a single die feels a little finicky to me. I would much rather have exploding dice everywhere or nowhere and just live with 1d6 not giving me an option for a full success.


One little idea I’ve been throwing around with an advantage mechanic is instead of “advanced” moves, include a move that is powerful but only triggers off of rolling 6s on the dice, regardless of the outcome. It’s a move that doesn’t necessarily reward high stats but does reward seeking advantage wherever you can.


You got it right.

You can absolutely ignore the little extra rule for 1d6 if you want to and it will still play fine, you would need to include the other rule though if you want the equivalent of a -2 roll.

Here’s the numbers behind it:


For completion’s sake, here’s the numbers for RAW 2d6 PBTA.PBTARAW


When I first posted this I wasn’t expecting to get answers that would completely change how I’m going to design PBTA from now on, but if you can roll more dice why wouldn’t you?? Thanks @BrianAshford and @William_Nichols for all this work (and you guys did it so fast?!?!) I think having a dice pool also makes advantage/disadvantage easier to keep track of if you do one 5+ to succeed with advantage and three 5+'s to succeed with disadvantage. I am really enjoying this discourse :grinning:

1 Like

I’m happy to help!

Applying Advantage and Disadvantage to this dice pool system in that way could be problematic. If Advantage means that you only need one 5+ for a full success then you won’t get any complications on Advantage. If you are asking for three dice rolling 5+ when you have disadvantage then the opposite happens and basically all successful rolls with be pass with complications. That might be OK for some games but if Advantage and Disadvantage are basically handed out as the GM sees fit it might start to feel like the GM is just choosing if you should have a full or partial success this time.

If it were me, I think I would just have Advantage add another dice to the pool and Disadvantage remove one. It might seem a little less interesting but it’s easier to understand and it’s closer to what those terms generally mean.

An other option would be to change the target for each dice. Advantage could be 4+, Disadvantage 6+. This would be a pretty huge effect though. Probably worth as much as +2/-2.


Personally, I’m a fan of things being as simple as possible, but no simpler.

Having a single system - Increasing and decreasing the dice pool – seems pretty simple. With the additional rule of with 1 dice you have a chance to get a second chance, and that if you need less than one dice you change the success target number, I think we’ve got something pretty simple.

Yes, I think so. The two exceptions are both only going to be used occasionally, and they can both be pitched as bonuses to help the player so that so make their addition more welcome. Also any fiddlyness would be more than compensated for by the fact that there is no maths required.

1 Like


Brian enjoyed doing the math, and I enjoy seeing projects get done. This is essentially my solution to any problem: find someone who wants to do it, and support then until we have a solution.

Most of my adult life has been figuring out new ways to support people.

1 Like

Currently, I have pondered quite a bit over combinations of modifiers and similar difficulty tools. I prefer either one or the other, implemented as simple as possible. The big questions one should ask oneself, I think, is why a certain mechanic is used, and what the player takeaway is from using it. There are trends coming and going, surely, but what is the design goal? Is it to create a more nuanced range of outcomes? A more unpredictable outcome? A smoother resolution process?

1 Like

There’s also the question of how opaque multiple types of roll modifiers get. As an example: I love the Marvel Heroic RPG, but some of the ways it allowed you to manipulate rolls left me unsure of why or when to use them. I didn’t have a feel for how they affected the probabilities, particularly when multiple mods were used on one roll.


I kind of prefer the approach of good old AW, where if you had it easier, you didn’t even have to roll, and if you had it too hard, you didn’t trigger the move and had to reposition to find another way. And in the middle, when you rolled dice, it felt risky enough and a failure meant I could land a hard move without holding my hand.
Consider that in BitD, the 3 positions don’t affect the odds of success and failure, they only controll what happened in each case.


In the science fiction-themed PBTA I am working on now, I have a few mechanics that let players roll 3 dice and use the best two. They are always for “super human” effects such as cybernetic upgrades or alien powers. The extra die only comes in during certain carefully prescribed instances such as “when you rely upon your brute strength.” Yes, the player can make sure they rely upon their brute strength a great deal in order to get the extra die, but I am OK with this, since super strong characters often do rely upon their strength. The GM does act as a backstop however, and has the ability to say “I don’t think this is a brute strength move,” so in a way, it does still come down to the GM granting it. Food for thought.