Your Armor Class (AC) represents how hard it is for opponents to land a solid, damaging blow on you. It's the Attack Roll result that an opponent needs to achieve to hit you. Your AC is equal to the following:

Pros Some Barbarians like to get their hands dirty, and making a natural attack based warrior is very possible. With the beast totem, you already have claws, meaning you really only need a bite. Natural Attacks are weird. The pathfinder rules break down what happens. Instead of using the iterative attacks from your base attack bonus, you get a full attack made up of all the natural attacks. The particular bonus depends on whether those attacks are considered primary.

10 + armor bonus + Shield bonus + Dexterity modifier + other modifiers

Note that armor limits your Dexterity bonus, so if you're wearing armor, you might not be able to apply your whole Dexterity bonus to your AC (see Table: Armor and Shields).

Automatic Misses and Hits: A natural 1 (the d20 comes up 1) on an attack roll is always a miss. A natural 20 (the d20 comes up 20) is always a hit. A natural 20 is also a threat—a possible critical hit (see the attack action).
Pros Some Barbarians like to get their hands dirty, and making a natural attack based warrior is very possible. With the beast totem, you already have claws, meaning you really only need a bite.

Sometimes you can't use your Dexterity bonus (if you have one). If you can't react to a blow, you can't use your Dexterity bonus to AC. If you don't have a Dexterity bonus, your AC does not change.

Other Modifiers: Many other factors modify your AC.

Enhancement Bonuses: Enhancement bonuses apply to your armor to increase the armor bonus it provides.

: Magical Deflection effects ward off attacks and improve your AC.

Natural Armor: If your race has a tough hide, scales, or thick skin you receive a bonus to your AC.

Pathfinder Natural Attacks Damage Reduction

Dodge Bonuses: Dodge bonuses represent actively avoiding blows. Any situation that denies you your Dexterity bonus also denies you dodge bonuses. (Wearing armor, however, does not limit these bonuses the way it limits a Dexterity bonus to AC.) Unlike most sorts of bonuses, dodge bonuses stack with each other.

Table: Size Modifiers

Size	Size Modifier
Colossal	–8
Gargantuan	–4
Huge	–2
Large	–1
Medium	+0
Small	+1
Tiny	+2
Diminutive	+4
Fine	+8

Size Modifier: You receive a bonus or Penalty to your AC based on your size. See Table: Size Modifiers.

Pathfinder Natural Attacks Full Attack

Touch Attacks: Some attacks completely disregard armor, including shields and natural armor—the aggressor need only touch a foe for such an attack to take full effect. In these cases, the attacker makes a touch Attack Roll (either ranged or melee). When you are the target of a touch attack, your AC doesn't include any Armor bonus, Shield bonus, or natural armor bonus. All other modifiers, such as your size modifier, Dexterity modifier, and Deflection bonus (if any) apply normally. Some creatures have the ability to make Incorporeal touch attacks. These attacks bypass solid objects, such as armor and shields, by passing through them. Incorporeal touch attacks work similarly to normal touch attacks except that they also ignore cover bonuses. Incorporeal touch attacks do not ignore armor bonuses granted by force effects, such as Mage Armor and bracers of armor.