Unarmoured Defense and Mage Armor

[Roflberries]

Can someone more familiar to DnD's ruleset clarify whether these should or should not work together?

In game they don't, the larger bonus takes effect. But I see nothing in the wording that explains why. Mage Armor adds 3 to your base armor class, and Unarmored Defense adds your wisdom/constitution (monk/barbarian) modifier to your armor class.

-edit- Draconic Resilience also does not work with Mage Armor.

[dustin1280]

So if you look at the actual wording of mage armor, it is as follows:
"Surround a creature in a protective magical force. Its Armour Class is set to 13 + Dexterity modifier."

That is not the same as adding 3 to your AC.

It actually changes your BASE armor calculation to be 13+Dex instead of 10+Dex.

Likewise if you look at the definition of unarmored defense
"While you are not wearing any armor, your Armor Class equals 10 + your Dexterity modifier + your Constitution modifier. You can use a shield and still gain this benefit."

That ALSO changes your core BASE AC calculation...

The golden rule of DnD 5e is nothing from the same source stacks.

Since BOTH change your core, base armor class, they do not stack.

Now look at the shield spell:
"When you are about to be hit by an enemy, increase your Armour Class by 5. You take no damage from Magic Missile."

That doesn't change your base armor calculation, it simply adds AC. So that would stack.

Edit:
Draconic Resilience also changes your base AC, in fact draconic resilience is basically the same as having mage armor on at all times.

[Mizu]

My understanding is that 5E doesn't let you stack some methods of increasing your AC that are too easy to access because they wanted to avoid people pushing their AC into the stratosphere.

[Roflberries]

Originally posted by dustin1280:

Likewise if you look at the definition of unarmored defense
"While you are not wearing any armor, your Armor Class equals 10 + your Dexterity modifier + your Constitution modifier. You can use a shield and still gain this benefit."

That ALSO changes your core BASE AC calculation...

That clarifies it, just a tool tip that could be worded better. Unarmored Defense doesn't specifically state that it's changing the base AC, which is what threw me off.

Cheers.

[zero]

the shorthand is this:

all 3 provide a *formula* to use, whichever one is better will be applied, they do not stack.