How do Expertise and the Acrobat feat proficiency effects combine? [duplicate]

Scenario : I make a character (rogue) and put proficiency in acrobatics, at level 1 I get expertise and double my acrobatics proficiency buff. (text from roll20):

Your proficiency bonus is doubled for any ability check you make that uses either of the chosen proficiencies.

At level 4, I then decide to take the Acrobat feat:

You gain proficiency in the Acrobatics skill. If you are already proficient in the skill, you add double your proficiency bonus to checks you make with it.

They are worded differently, the expertise class skill says to double my existing proficiency bonus before adding it while the acrobat feat says I get to double what I add to my skill check proficiency bonus.

Does this mean I can get +8 to my proficiency modifier or no? I looked at past related topics and all of them seemed to be asking about doing this through 2 class abilities by dual classing, save for one. That one was labeled a duplicate and unanswered and then linked to an old question about using 2 different class abilities to meet a similar result. This is through 1 class ability and then a feat. Does that not make a difference?

The equation is the same regardless of how it'd be ordered correct?

• 1d20 + (3 ability score + ((2 prof + 2 feat) × 2 expertise) or

• 1d20 + (3 ability score + ((2 prof × 2 expertise) + 4 feat)

The common answer is "you still only add it once and multiply it once" If this is correct then how is it not doable? Expertise doubles you bonus while the feat adds it twice. Is that not different to doubling it twice?

The end result is Expertise makes your proficiency bonus double where applied for that skill by default, the feat specifically states to add that proficiency bonus to the skill twice. Is that not how it is worded?

I do not think Jeremy Crawford's answer that is being quoted is correct in this scenario; you are not multiplying the proficiency twice, you are multiplying it once(which doubles the prof bonus) and then add that result twice as the feat says you do.

If you can not do this, then that would mean the feat is not able to apply regardless of having expertise because the feat specifically states for you to add your proficiency modifier twice to your roll.

• @NautArch Not a duplicate since it's asking about expertise/feat not expertise/expertise Jun 15, 2017 at 15:31
• @Conduit I wasn't sure because while the specifics differ, the effects remain the same. The no stacking applies because the end modification of expertise vs the feat is the same. But happy to have it in here to make it more easily found for this specific case if it's not a dupe. Jun 15, 2017 at 15:33
• @NautArch good intuition, in any case. Pretty sure it's disallowed by the same rule. Jun 15, 2017 at 15:34
• A consideration: not all feats apply or are relevant to all characters. Some create redundancies like the one you have. You could also say that Heavily Armored doesn't apply to Fighters/Paladins or anyone with Heavy Armor Proficiency already. But both Heavy Armored and Acrobatics provide other benefits which still apply and may be useful. Jun 15, 2017 at 15:59
• @Clarus_Nox In some rare cases we do duplicate older questions to newer ones. You can see in this meta why it was done in this case. Nov 28, 2018 at 19:36

They do NOT stack. If you have Expertise, taking a Feat to allow you to add double your proficiency bonus does not let you quadruple your Proficiency Bonus.

Q: for the second part of the feat, it says add double the proficiency bonus. How does that stack with expertise?

A: You never add or multiply your proficiency more than once when you apply it to a roll. For more, see "Proficiency Bonus" (PH, 173–4).

And his reference into the PHB says this...

Occasionally, your proficiency bonus might be multiplied or divided (doubled or halved, for example) before you apply it. For example, the rogue's Expertise feature doubles the proficiency bonus for certain ability checks. If a circumstance suggests that your proficiency bonus applies more than once to the same roll, you still add it only once and multiply or divide it only once.

Emphasis Mine

This was then followed by a request for further clarification:

Q: This doesn't answer. Expertise and Feat double Proficiency. The final Prof. is only added once, but do the doublings stack?

So, this is Jeremy Crawford, who is the voice of Official Rulings from WotC saying that Skill Feats and Expertise Do Not Stack. Regardless of how you try to phrase the equation.

Bear in mind that Unearthed Arcana is playtest material that has not been gone over with a fine-toothed comb to make sure it perfectly conforms to everything in the primary rule books. There will be weird things in there like inconsistent wording. This is likely why Crawford had to make this ruling in the first place...and it's a fair guess that, should we see these Feats in a future rulebook, the wording will be updated to match the phrasing used in the Expertise feature to clear up any confusion.

I would also note, as an aside...that being able to effectively quadruple your Proficiency Bonus is insanely OP. 5E, in the DMG, generally caps DCs at 30. If you could double up with a Feat and Expertise (and it's your primary stat), you're looking at a +29 to a skill by max level. Whereupon it is literally impossible for you to fail if the DM keeps DCs within the normal range and maintains the 'fumbles are not a thing for Skill Checks' rule. Expertise is powerful enough on its own. Even if Crawford hadn't made the above ruling...I would absolutely ban that attempt from any table I ran.

• Comments are not for extended discussion; this conversation has been moved to chat.
– nitsua60
Jun 15, 2017 at 17:31
• Are you implying the UA eventually always goes through a "fine tooth comb" Looks at Twilight and Tempest Clerics Wonders what combs Crawford and them even have Dec 14, 2021 at 8:55
• @SpiderWaffle Fair enough...I guess some of their combs are missing some teeth Dec 14, 2021 at 13:18

You cannot get better than double this way

If a circumstance suggests that your proficiency bonus applies more than once to the same roll, you still add it only once and multiply or divide it only once. (PHB 174)

Also note that the feat does not modify your proficiency bonus, it replaces the number you add to your check with 2xPB. In that regard it is similar to how armors replace your base AC and not modify it.