Does a Tortle benefit from unarmored defense?

There is nothing that says the Tortle cannot benefit from unarmored defense. Also note that Shell Defense stacks with whichever AC calculation you choose because it is a bonus and not a calculation.

Does natural armor stack with Monk?

To answer your question – the tortle natural armor and the monk’s unarmored defense do not “stack” or in any way combine with each other – as with all AC calculations, you select which one you want to use.

Does natural AC stack with armor?

They do stack. You can only use one item, ability, spell etc. that has a formula for calculating your baseline AC(armor that you wear, natural armor, the Mage Armor spell, Unarmored Defense, etc), but you can make use of multiple items that offer a “bonus” to AC, such as a shield, a Ring of Protection etc.

Does Ironskin stack with Amulet of natural armor?

Does this not stack with natural armor bonuses, say from an amulet of natural armor? Creature Natural Armor IS Natural Armor and they don’t stack. The enhancement bonus provided by barkskin stacks with the target’s natural armor bonus, but not with other enhancement bonuses to natural armor.

Does barkskin stack with Ironskin?

Don’t forget that the enhancement bonus to Natural armor doesn’t stack with other enhancement bonuses to natural armor. So Barkskin wouldn’t stack with Ironskin (http://www.d20pfsrd.com/magic/all-spells/i/ironskin)for example.

Does natural armor stack in Pathfinder?

A natural armor bonus improves armor class resulting from a creature’s naturally tough hide. Natural armor bonuses stack with all other bonuses to armor class (even with armor bonuses) except other natural armor bonuses. A natural armor bonus doesn’t apply against touch attacks.

What is natural armor?

Natural Armor is an AC calculation formula, not actual armor. When a Monk/Druid uses Wild Shape, they have the option of using either the Natural Armor calculation or the Unarmored Defense calculation. The decision to use one or the other does not interfere with the Unarmored Movement feature.