How is ac calculated?


Playing the Game

Liberty's Edge

Not sure on how ac is calculated. I know each character has proficiency in armor types that gets added to the item bonus. Are we just adding the plus or because it's a proficiency do I add my level as well?

For example a 10th level fighter in +1 chain shirt and 18 dex he has master in light armor, is his armor class 18 (+2 for armor, +1 for magic, +1 for master and +4 for dex) or is it 28 (+2 for armor, +1 for magic, +4 for dex and +11 for master proficiency)

Thanks.


I had this same question, by the letter of the rulebook it would seem that you would add your level so the AC would be 28 in your example.

I was unsure of this so I turned to the bestiary and found the NPC section toward the end. It was there i found the level 3 NPC Cleric of Rovagug who is wearing chain mail. In the NPC entry this cleric has a dex of +0 but an AC of 18. Seeing as chain mail provides a +4 there is still another +4 missing. It would be reasonable to assume that this cleric is an expert in medium armor but nothing higher as it is only a level 3 NPC which accounts for a +1 to AC. This leaves us at 15 AC. So it would dictate that we must also be adding this clerics 3 levels to AC giving us the 18 AC per the NPC Stat block.

In conclusion yes it would seem you add your level


The Armor and Shields section in equipment says, under Armor Class:

"Your Armor Class equals 10 plus your Dexterity modifier (up to your armor’s Dexterity modifier cap) plus your proficiency modifier for any armor or shield you are using plus the armor’s item bonus to AC."

Then, page 8, under Proficiency Modifier, describes all the Proficiency Modifiers you have. They are all Level+Something. For example:

"If you’ve been trained in the statistic or item, your proficiency modifier is equal to your level.

As an expert, you are highly trained in the statistic or item. Your proficiency modifier is equal to your level plus 1.'

So yes, you add your Level to Armor Class, because Level is part of your Proficiency Modifier.


Now ask what your AC is if you are not wearing armor.

10 + dex + 0 for no armor + proficiency??? Monks are experts in unarmored defense. Sorceers and wizards are apparently untrained in this proficiency. (Animal companions are trained in unarmored defense)

Page 176: If you’re not wearing armor, substitute your proficiency in unarmored defense.

So the Monk with Dex 14 is 10 + 2 + 0 + 2 (expert + level 1) = 18 AC
and wizard with Dex 14 is 10 + 2 + 0 - 1 (untrained + level 1) = 15 AC

And unarmored defense is not listed in the armor section of the character sheet.


Unarmored is its own proficiency (and monks are the only ones that get any training in it).

You're right that its not represented on the character sheet though.


Expect the sample wizard apparently IS trained in unarmored defense. It's just a known hole in the rules. People mostly just assume wizards and sorcerors are trained in ud, but how about rogues who want to be swashbucklers?


Draco18s wrote:

Unarmored is its own proficiency (and monks are the only ones that get any training in it).

You're right that its not represented on the character sheet though.

looking at the npc's in the bestiary there is a demonologist who is not wearing armour... ac is 19 at level 5 with a dex mod of +3...

maths 10 + armour bonus + dex + armour proficiency = ac.
10+0+3+x=19
x = 6
so if they are expert in unarmoured defence then it would be 1 + level. this seems to be correct but there is no listing for why a sorcerer or wizard would get expert in unarmoured defence. also I see no feat that allows it either.

it would be nice in paizo would clarify this.


Harrythefish wrote:
Draco18s wrote:

Unarmored is its own proficiency (and monks are the only ones that get any training in it).

You're right that its not represented on the character sheet though.

looking at the npc's in the bestiary there is a demonologist who is not wearing armour... ac is 19 at level 5 with a dex mod of +3...

maths 10 + armour bonus + dex + armour proficiency = ac.
10+0+3+x=19
x = 6
so if they are expert in unarmoured defence then it would be 1 + level. this seems to be correct but there is no listing for why a sorcerer or wizard would get expert in unarmoured defence. also I see no feat that allows it either.

it would be nice in paizo would clarify this.

The Demonologist has, under spells "mage armor (already cast)" as a 1st level spell, which would explain the missing +1. Because then you have:

10+3 (Dex)+ 5 (Level) + 1(Mage Armor).

However, Mage Armor says you use your Unarmored Defence Proficiency and, as written, nobody gets it except the Monk, so RAW that AC should be 2 points lower, since the Demonologist is Untrained.

The stats assume he's Trained though, so I figure that's the idea.

The Exchange

Hm... I'm curious as to how this will play out once I can get my group together. Armor Class and To-hit bonuses scaling at the same rate makes it seem like you'll always be looking for the same number to come up on your d20 assuming you're facing an appropriate challenge. It is interesting though, as in 1E, armor class kinda fell apart at higher levels simply because AC couldn't keep up with attack rolls and limiting the number of attacks aimed at you became more important than the dice being rolled.


That's quite an oversight: not allowing any way via feats to gain proficiency in Unarmored Defence. Or just give wizards and cloth casters 'trained in unarmored defence' for free.

Or perhaps it's intended to be there as a way to keep caster ACs lower?


Joe Mucchiello wrote:

Now ask what your AC is if you are not wearing armor.

10 + dex + 0 for no armor + proficiency??? Monks are experts in unarmored defense. Sorceers and wizards are apparently untrained in this proficiency. (Animal companions are trained in unarmored defense)

Page 176: If you’re not wearing armor, substitute your proficiency in unarmored defense.

So the Monk with Dex 14 is 10 + 2 + 0 + 2 (expert + level 1) = 18 AC
and wizard with Dex 14 is 10 + 2 + 0 - 1 (untrained + level 1) = 15 AC

And unarmored defense is not listed in the armor section of the character sheet.

...so by the same token, a Wizard COULD wear armor, he is just -2 lower AC, with no other penalties (other than armor check to certain skills), correct?

So the level 1 wizard in your example could pick up leather armor and have no penalties from it and be 1 point higher?

Also, how does 10 (base) +2 (dex) + 0 (unarmored) -2 (untrained) +1 (level) = 15? Should that not be AC 11? Am I missing something?

Scarab Sages

Pathfinder Maps Subscriber; Pathfinder Roleplaying Game Superscriber
Joe Mucchiello wrote:

So the Monk with Dex 14 is 10 + 2 + 0 + 2 (expert + level 1) = 18 AC.

Am I missing something or isn't this AC 14?


zer0darkfire wrote:
Joe Mucchiello wrote:

So the Monk with Dex 14 is 10 + 2 + 0 + 2 (expert + level 1) = 18 AC.

Am I missing something or isn't this AC 14?

Here is the correct calculation for the AC

Level 1 Monk with Dex 14 =
10 + 2(Dex) + 0(Item) + 2(expert + Level) = 14 AC

Level 1 Wizard with Dex 14 =
10 + 2(Dex) + 0(Item) - 1 (untrained + Level) = 11 AC

Grand Lodge

Pathfinder Starfinder Adventure Path, Starfinder Society Subscriber

All classes are trained in unarmored.


OK. I am trying to follow this to get everything down because I am also a bit confused on this area. I have not picked up the Bestiary yet, as I am still rolling through the main tome.

Is the Dexterity Modifier simply each point over 12 Dexterity or am I looking at this incorrectly as all examples above have 14 Dexterity listed?

Damanta, if all classes are trained in unarmored; would that put the final modifier at 1 then in your opinion?

Sorry. I have been out of gaming for some time and the area of Armor Class and stat modifiers feels oddly incomplete. With that, I appreciate any assistance in these matters.

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