Natural Armor: How does it work?

[supergoji18]

I'm really confused on how natural armor works in 5e for monsters. I can't find any way to properly calculate their natural armor bonuses, and it's been getting on my nerves.

Here's a few examples:

Ancient Red Dragons have an armor class of 22. This means that somewhere, they got a +12 bonus to their armor class. Where does this bonus come from? I've tried doing a bunch of different methods, but none seem to add up quite right.
This only gets worse when you realize that Ancient Gold Dragons have the same armor class, despite having 14 Dex and higher stats overall. So no matter what, the AC should be at least 2 higher than that of the red dragon's. But it's exactly the same.
And then there are the younger versions of Red Dragons. Wyrmlings get base 17 armor class (still trying to figure that one out). They get a +1 bonus to it every age category... until Ancient where it shoots up to +3.

Is natural armor just an arbitrary bonus the game-makers give? If not, how is it determined?

[coredump]

You are over thinking it. Nat Armor is just the AC boost they get from the toughness of their skin/hide/whatever. It will be different for each creature, and they never really state what it is for any particular creature.

You can likely deduce it from their AC and Dex mod.....

[SharkForce]

not even necessarily an arbitrary bonus; it is entirely probable that it works like heavy armour and simply sets your armour class to a certain value rather than being any sort of bonus at all.

[CodeRed]

Natural armor doesn't exist anymore in my opinion. Monster AC is an arbritrary number set by the designer/DM in accordance with what feels right for the CR/monster. The guidelines in the back of the DMG lay it out pretty well. A monster with higher damage should have a lower AC for the same CR, a "defensive" type should have higher. As to the dragons, the Red Wyrm and Gold Wyrm are 22 AC despite having different Dex scores just because 22 is a good number for that CR.

[RickAllison]

I just tweeted (is that the correct past form for tweet?) JC about whether it is a modifier or a recalculation method. As for the values themselves, I have found neither rhyme, nor reason.

[JackPhoenix]

I just tweeted (is that the correct past form for tweet?) JC about whether it is a modifier or a recalculation method. As for the values themselves, I have found neither rhyme, nor reason.

You can just check Sage Advice: http://www.sageadvice.eu/2015/10/31/natural-armor-shield/, http://www.sageadvice.eu/2015/01/29/natural-armor/, http://www.sageadvice.eu/2014/09/02/natural-armor-cap/.

[RickAllison]

You can just check Sage Advice: http://www.sageadvice.eu/2015/10/31/natural-armor-shield/, http://www.sageadvice.eu/2015/01/29/natural-armor/, http://www.sageadvice.eu/2014/09/02/natural-armor-cap/.

Got it, I couldn't find that first one which was the relevant tweet (the other two weren't really applicable).

[Vogonjeltz]

I'm really confused on how natural armor works in 5e for monsters. I can't find any way to properly calculate their natural armor bonuses, and it's been getting on my nerves.

Here's a few examples:

Ancient Red Dragons have an armor class of 22. This means that somewhere, they got a +12 bonus to their armor class. Where does this bonus come from? I've tried doing a bunch of different methods, but none seem to add up quite right.
This only gets worse when you realize that Ancient Gold Dragons have the same armor class, despite having 14 Dex and higher stats overall. So no matter what, the AC should be at least 2 higher than that of the red dragon's. But it's exactly the same.
And then there are the younger versions of Red Dragons. Wyrmlings get base 17 armor class (still trying to figure that one out). They get a +1 bonus to it every age category... until Ancient where it shoots up to +3.

Is natural armor just an arbitrary bonus the game-makers give? If not, how is it determined?

Natural armor is like wearing armor. So the scheme for dragons appears to be: X, X+1, X+2, X+5 for Wyrmling, young, adult, ancient; respectively.

Hem this applies to most dragons, some only add +4 for the ancient, perhaps because they are traditionally weaker types.