Armor Class Optimization


  • PC

    Best Light Armors
    Chain shirt: +4 AC, max +4 Dex, ACP -2, 20% spell failure (100gp)
    Mithral breastplate: +5 AC, max +5 Dex, ACP -1, 15% spell failure. (4,200 gp)
    Skin of Ectoplasmic Armor: +8 AC, max +2 Dex, ACP -6, 25% spell failure. (6,000 gp)
    Celestial Armor: +8 AC, max +8 Dex, ACP -2, 15% spell failure. (22,400 gp)
    Weightless Celestial Armor: +8 AC, max +10 Dex, ACP 0, 5% spell failure. (29,400 gp)
    Weightless Celestial Armor +2: +10 AC, max +10 Dex, ACP 0, 5% spell failure. (49,400 gp)
    Armor of the Celestial Battalion: +12 AC, +10 Dex, ACP 0, 10% spell failure (616,300gp)

    Best Medium Armors
    Dragonscale Husk: +6 to +12 AC, max +2 Dex, ACP -4, 0% spell failure. You need to take 1 level of Figher/Cleric (or any class with heavy armor proficiency). May require taking the Dragontouched feat. (0 gp)
    Breastplate: +5 AC, max +3 Dex, ACP -4, 25% spell failure. (200 gp)
    Mithral Full Plate Armor: +8 AC, max +3 Dex, ACP -3, 25% spell failure. (10,500 gp)
    Mithral Heavy Plate: +9 AC, max +2 Dex, ACP -5, 45% spell failure. (11,000 gp)
    Mithral Mechanus gear: +10 AC, max +2 Dex, ACP -7, 40% spell failure, -5 movement. (10,750 gp)
    Mithral Full Plate Armor +1 of Nimbleness: +9 AC, max +5 Dex, ACP -2, 25% spell failure. (16,150gp)

    Best Heavy Armors
    Full plate: +8 AC, max +1 Dex, ACP -6, 35% spell failure. (1,500 gp)
    Mechanus gear: +10 AC, max +0 Dex, ACP -10, 50% spell failure, 15 base movement. (1,750 gp)
    No Spell Failure Armor/Shield (or equivalent)
    Dragonscale Husk: +6 AC, max +2 Dex, ACP -4, 0% spell failure. You need to take 1 level of Figher/Cleric (or any class with heavy armor proficiency). May require taking theDragontouched feat. (0 gp)
    Mithral Buckler: +1 AC, ACP 0, 0% spell failure. (1,015g)
    Feycrafted Darkwood Buckler, +1, ACP 0, 0% spell failure. (715gp)
    Bracers of armor: +1 AC. (1,000 gp)
    Bracers of armor: +5 AC. (25,000 gp)
    Twilight Mithral Chain Shirt +1: +5 AC, max +6 Dex, ACP -0. (5,100gp)
    Luminous Armor spell.
    Twilight Mithral Thistledown-suited Breastplate +1: +6 AC, max +6 Dex, ACP -1, (8,050 gp)

    ACP0 Armor
    A character who wears armor and/or uses a shield with which he or she is not proficient takes the armor’s (and/or shield’s) armor check penalty on attack rolls and on all Strength-based and Dexterity-based ability and skill checks. But these all have an ACP of zero so no penalty, hence anyone can use these.

    Leather: +2 AC, ACP 0, 10% spell failure. (10gp)
    Darkwood Buckler: +1 AC, ACP 0, 5% spell failure. (65gp)
    Darkwook Sheild, Heavy Wooden: +2 AC, ACP 0, 15% spell failure (107gp)
    Mithral Shirt: +4 AC, ACP 0, 10% spell failure. (1,000gp)
    Mithral Breastplate +1 of Nimbleness: +6 AC, ACP 0, 25% spell failure (8,300gp)
    Weightless Celestial Armor: +8 AC, +10 Dex, ACP 0, 5% spell failure. (29,400 gp)
    Armor of the Celestial Battalion: +12 AC, +10 Dex, ACP 0, 10% spell failure (616,300gp)
    Luminous Armor spell.

    Feats
    Dodge gives a +1 dodge bonus to AC. Dodge always stacks.
    Battle Caster allows Warlocks (ability to cast in light armor) to cast in medium armor.
    Battle Sorceror: Allows Sorcerer to cast in light armor.

    Spells that improve your AC
    Using Permanency or Persistent Spell can dramatacily increase the effectiveness of these spells.

    Alter Self: varies (consider troglodyte)
    Barkskin: +2 to +5 enhancement to natural armor.
    Mage Armor: +4 AC, 1 hr per caster level.
    Mage Armor, Greater
    Blurr: 20% miss chance
    Displacement: 50% miss chance
    Bigby’s Interposing Hand: +4 cover AC
    Protection from Evil: +2 deflection against evil creatures
    Shield: +4 shield
    Shield of Faith: +2 to +5 deflection bonus
    Halo of Sand: +1 to +4 deflection bonus
    Magic Vestment: +1 to +5 enhancement bonus
    Improved Invisibility: 50% miss chance.
    Luminous Armor: +5 AC, max Dex, ACP 0, 0% spell failure.
    Luminous Armor, Greater: +8 AC, max Dex, ACP 0, 0% spell failure.
    Magic Vestment: +1 to +5 enhancement bonus.
    Righteous might: +2 bonus natural armor.
    Spider skin: +1 to +5 natural armor.
    Dragonskin: +1 to +5 natural armor.
    Bite of the X: various natural armor.
    Divine agility: +10 Dex.
    Scintillating scales: Changes natural to deflection.
    Armor of Darkness: +4 to +8 deflection.
    Foresight: +2 insight
    Haste: +1 dodge
    Visions of the future: +1 dodge
    Exalted rainment: +1 sacred per 5CL.
    Interfaith blessing: +1 to +2
    Shield of Warding: +1 sacred per 5CL.
    Holy Star: +6 circumstance.
    Silver beard: +2 sacred
    Sacred haven: +2 sacred
    Divine protection: +1 morale
    Recitation: +2 to +3 luck

    Misc Items that improve your AC
    Amulet of natural armor: +1 natural. (2,000 gp)
    Ring of protection: +1 deflection. (2,000 gp)
    Gloves of Dexterity: +2 dex. (4,000 gp)
    Ioun stone, dusty rose: +1 insight. (5,000 gp)
    Belt, Monk’s: If wearing no armor/shield you can add wisdom bonus +1 to AC. (13,000 gp)
    Crystal of Arrow Deflection: +2 deflection vs ranged attacks. (250 gp)
    Defending Gauntlets +1: +1 to AC (8,000 gp)
    Ironhorn extract: +1 bonus for 1 week. 25gp
    Staff of Power: +2 luck bonus to AC. 4,220 gp for a staff with 1 charge left.

    Misc
    Fighting defensively gives you +2 bonus to Armor Class, although you take a -4 penalty on attacks. Taking Combat Expertise can improve this further. Unfortunately this only works for attack actions not casting spells.
    Flying while using ranged attacks allows you to avoid most powerful melee attacks.
    Flying while invisible is almost too perfect. Your basically untouchable unless your foe can bypass your invisibility.
    Cloak of displacement: 20% is equivalent to +4 AC, 50% is equivalent to +10 AC. These work with existing armor too!
    Using a reach weapon (such as a Chain, Spiked) combined with Improved Trip can be very effective.
    Hiding is almost like being invisible.
    Mithralmist Shirt allows you hide anywhere. (3,400 gp)


  • PC

    Item Price
    +1 enhancement 1,000 gp
    +1 deflection/natural 2,000 gp
    +2 enhancement 3,000 gp
    +2 Dexterity (+1 AC) 4,000 gp
    +3 enhancement 5,000 gp
    +1 insight (ioun stone) 5,000 gp
    +2 deflection/natural 6,000 gp
    +4 enhancement 7,000 gp
    +5 enhancement 9,000 gp
    +3 deflection/natural 10,000 gp
    +4 Dexterity (+2 AC) 12,000 gp
    +4 deflection/natural 14,000 gp
    +5 deflection/natural 18,000 gp

  • PC

    Sample Fighter AC Progression

    The following is presented to show typical AC and To-Hit scores for an average fighter. The following assumptions have been made:

    Uses a 1 handed weapon and shield
    Starting Dexterity of 13 (+1 modifier)
    Starting Strength of 16 (+3 modifier)
    To-hit bonus will increase every 3 levels (Strength, magic weapon, feats)

    Level Net Worth Armor Budget To-Hit Armor Class
    1 200 gp 120 gp +4 18 (+4 Scale mail, +2 Shield, +1 Dex, +1 Dodge)
    2 900 gp 270 gp +5 20 (+6 Banded mail, +2 Shield, +1 Dex, +1 Dodge)
    3 2,700 gp 1,520 gp +7 22 (+8 Full plate, +2 Shield, +1 Dex, +1 Dodge)
    4 5,400 gp 2,520 gp +8 23 (+9 Full plate+1, +2 Shield, +1 Dex, +1 Dodge)
    5 9,000 gp 3,520 gp +9 24 (+9 Full plate+1, +3 Shield+1, +1 Dex, +1 Dodge)
    6 13,000 gp 5,520 gp +11/+6 25 (+9 Full plate+1, +3 Shield+1, +1 Dex, +1 Dodge, +1 Deflection)
    7 19,000 gp 7,520 gp +12/+7 26 (+9 Full plate+1, +3 Shield+1, +1 Dex, +1 Dodge, +1 Deflection, +1 Natural)
    8 27,000 gp 13,520 gp +13/+8 28 (+10 Full plate+2, +4 Shield+2, +1 Dex, +1 Dodge, +1 Deflection, +1 Natural)
    9 36,000 gp 18,520 gp +15/+10 29 (+11 Full plate+3, +4 Shield+2, +1 Dex, +1 Dodge, +1 Deflection, +1 Natural)
    10 49,000 gp 23,520 gp +16/+11 30 (+11 Full plate+3, +5 Shield+3, +1 Dex, +1 Dodge, +1 Deflection, +1 Natural)
    11 66,000 gp 28,520 gp +17/+12/+7 31 (+11 Full plate+3, +5 Shield+3, +1 Dex, +1 Dodge, +1 Deflection, +1 Natural, +1 insight)
    12 88,000 gp 40,520 gp +19/+14/+9 33 (+11 Full plate+3, +5 Shield+3, +1 Dex, +1 Dodge, +2 Deflection, +2 Natural, +1 insight)
    13 110,000 gp 54,520 gp +20/+15/+10 35 (+12 Full plate+4, +6 Shield+4, +1 Dex, +1 Dodge, +2 Deflection, +2 Natural, +1 insight)
    14 150,000 gp 72,520 gp +21/+16/+11 37 (+13 Full plate+5, +7 Shield+5, +1 Dex, +1 Dodge, +2 Deflection, +2 Natural, +1 insight)
    15 200,000 gp 92,520 gp +23/+18/+13 39 (+13 Full plate+5, +7 Shield+5, +1 Dex, +1 Dodge, +3 Deflection, +3 Natural, +1 insight)
    16 260,000 gp 117,520 gp +24/+19/+14/+9 41 (+13 Mithral Full plate+5, +7 Shield+5, +3 Dex, +1 Dodge, +3 Deflection, +3 Natural, +1 insight)
    17 340,000 gp 163,520 gp +25/+20/+15/+10 44 (+13 Mithral Full plate+5, +7 Shield+5, +3 Dex, +1 Dodge, +5 Deflection, +4 Natural, +1 insight)
    18 440,000 gp 181,520 gp +27/+22/+17/+12 45 (+13 Mithral Full plate+5, +7 Shield+5, +3 Dex, +1 Dodge, +5 Deflection, +5 Natural, +1 insight)
    19 580,000 gp +28/+23/+18/+13
    20 760,000 gp +30/+25/+20/+15/+10

  • PC

    Now there are some credible arguments about the different types of defenses, normally i would say not to put to much investment into AC. Several opinions about this, but depending on the DM, i would rank them in this order of importance.

    1. HP: Protects against everything
    2. Saves: Protects against magic
    3. Miss chance (blur, concealment, invisibility, displacement): Protects against all physical & touch attacks, no matter what the attack’s to-hit roll is
    4. AC: Protects against non-touch attacks where the attacker doesn’t have a massive to-hit bonus (dragon, big golem, etc).