Ok, I realize that I have been away from RPGs, a LONG time, when I tried to understand the interaction of various armor and things that give you armor.

Old school, they use to try and build tanks, by having magical armor, stacked with magical braces, stacked with magical rings, etc.

But in reading Pathfinder (and I guess version 3.x of dnd) there are now things that do and don't or can and can't stack to give resulting armor.

But I don't see a simple explanation:

This can stack with this, this can't.

You know a flow chart!

There seems to be a little assuming in the explanations that I read, can someone help me out?

The reason I ask, is that my character recently gained access to bracers of defense, but I'm not sure this is a good purchase for a fighter who wears armor.

thanks

As a general rule, different bonus types stack and same bonus types do not.

Armor grants an 'armor' bonus to AC.
Bracers of armor grant an 'armor' bonus to AC.
Therefore, these do not stack.
Now, in this case, keeping the bracers isn't necessarily a bad idea if you fight the incorporeal undead, as the bracers generate a 'force' effect that lets you apply their bonus to your AC against such critters. Normal armor, even most magical armor, doesn't do that. But otherwise, unless your bracers are pretty potent and your armor is not, they're not worth it.

Exception to the rule for same bonus types not stacking:
Dodge bonuses stack
Some circumstance bonuses stack, check with your DM
Bonuses without a name/type always stack

So long and short, don't wear bracers if you plan on wearing armor, its redundant.

So long and short, don't wear bracers if you plan on wearing armor, its redundant.

Or if wearing armor causes you problems in the society you're standing in.

Or if your character concepts favors the unarmored look.

The easiest way to remember it is this:

If the armor types are the same, they don't stack (except dodge and untyped).

If they're different, they stack.

In the below example, I'll give an example piece of equipment and put the type in parentheses.

So your rings of protection (deflection) stack with your Full Plate (armor), your boots (dodge), your Dodge feat (dodge), your class ability (usually insight), and your shield (shield).

If you were wearing leather armor and then found bracers of armor +5, your armor bonus would improve to 5 (not BY 5, but raise to 5).

This convention is the same for most other things in 3.x.

Skills (competence, enhancement, insight, etc types)
Ability scores
DR
Damage and to-hit bonuses...

The list goes on...

'Types' of armor class bonuses you might see...
Armor Bonus (Doesn't stack w/ other Armor bonuses)
Shield Bonus (Doesn't stack w/ other Shield bonuses)
Deflection Bonus (Doesn't stack w/ other Deflection bonuses)
Natural Armor Bonus (Doesn't stack w/ other Natural Armor bonuses)
Divine Bonus (Doesn't stack w/ other Divine bonuses)

**When something doesn't stack you get the better of the two.

-----------------
Dodge Bonus (Always stack)
Circumstance Bonus (May stack, DM's option usually)

-----------------
And a big one folks above missed...
'Defending' Magic Weapon Property Bonus (Stacks w/ EVERYTHING)

One minor detail that's been missed so far. Untyped bonuses (those without a name) only stack if they are from different sources.

Let's say there's a spell (Udalrich's AC Boost) that grants an (untyped) +2 bonus to the AC of the target. This will stack with armor, deflection and other typed bonuses. However, if I cast this spell on you twice, you only get a total of +2 to AC, not +4. (Casting twice isn't totally worthless, since the second one will start to apply if the first one expires or is dispelled, but that's rarely worth it.) Even if someone else cast Udalrich's AC Boost on you, it still wouldn't stack, since it's coming from the same spell (even though there's a different caster).

If there is a different spell (Miniature Peddler's AC Boost) that also grants an untyped +2 bonus to AC, then you would gain a total of +4 to AC if both spells were cast on you (even if the same caster did it) because the sources are different.

'Types' of armor class bonuses you might see...
Armor Bonus (Doesn't stack w/ other Armor bonuses)
Shield Bonus (Doesn't stack w/ other Shield bonuses)
Deflection Bonus (Doesn't stack w/ other Deflection bonuses)
Natural Armor Bonus (Doesn't stack w/ other Natural Armor bonuses)
Divine Bonus (Doesn't stack w/ other Divine bonuses)

**When something doesn't stack you get the better of the two.

-----------------
Dodge Bonus (Always stack)
Circumstance Bonus (May stack, DM's option usually)

-----------------
And a big one folks above missed...
'Defending' Magic Weapon Property Bonus (Stacks w/ EVERYTHING)

Just as an aside, the fun of playing a 3.5 druid was getting the stacking benefits of armor and natural armor while in wildshape (with Wild armor and shield, of course). My old druid had a mighty fine AC when buffed up and ready for "bear" (had to be said, sorry!).

But the point of saying that is to get you to keep track of what bonuses you have so you (or your DM) knows what stacks and what does not. Enjoy!