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AC in DnD 5E: How to calculate and improve armor class in 5E

It takes thick skin to be an adventurer. Plate mail-thick.

If you play a session of Dungeons & Dragons 5th Edition, you’re going to end up taking hits. Your Armor Class will be asked for over and over again, especially if you’re up front and personal with monsters.

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It’s one of the most commonly used aspects of your character sheet. But, once you can calculate it, you can figure out how to make it better. So, let’s armor up.

Armor Class, or AC, is a difficulty check that represents how hard you are to hit in 5E (and also Baldur’s Gate 3). In order to deal damage to someone with an attack roll, a character must roll equal to or higher than their target’s Armor Class. This defense applies to both weapon attack rolls and spell attack rolls.

How to find Armor Class (AC) in 5E

In order to calculate your AC, you will first have to figure out what the AC of your armor is—or 10, if you have no armor. Add your Dexterity modifier to the number given to you by your armor—to a maximum of two for Medium Armor and zero for Heavy Armor. Then, add any bonus AC from wearing a shield. Finally, add miscellaneous bonuses from effects such as spells, class features, or magical items.

The basic formula for AC looks like the following.

AC = Armor (or 10 if no armor) + Dexterity modifier + Shield bonus (if any) + Other bonus

Armors have a listed value for AC between 11 and 18. Shields provide a +2 to AC while they are worn on an arm.

Let’s look at a few examples to see how AC changes based on specific character builds from Baldur’s Gate 3, which uses the same AC system as DnD.

  • Gale, a Wizard with 13 Dexterity, has an AC of 11 (10 plus Dexterity modifier of one). If he casts Mage Armor—a spell that gives a default armor value of 13—his AC becomes 14 (13 plus Dexterity modifier of one).

Related: Baldur’s Gate 3: Best Wizard build in BG3

  • Shadowheart, a Cleric with 16 Dexterity, has an AC of 14. When she equips Scale Mail—Medium Armor with a default armor value of 14—her AC becomes 16 (14 plus Dexterity modifier of three, but Medium Armor caps Dexterity’s AC bonus at two). If she equipped a shield, her AC would become 18.
  • Lae’zel, a Fighter with 13 Dexterity, has an AC of 11. When she equips Plate Mail—Heavy Armor with a default armor value of 18—her AC becomes 18 (18 plus no Dexterity modifier due to Heavy Armor’s restriction). If she equipped a shield, her AC would become 20.

As a side note, a character can wear armor that they are not proficient in. However, doing so causes you to take disadvantage on ability checks, saving throws, and attack rolls that involve Strength or Dexterity. You also can’t cast spells while doing so. So, the Wizard Gale could wear Plate Mail to get that huge AC bonus, but he’d be not particularly useful in combat as a trade-off.

How to buff AC

A man looks at a skeleton adorned with armor in Baldur's Gate 3. The skeleton appears to be reanimated.
You’ll want solid AC, or you’ll end up like this guy. Image via Larian Studios.

Basic armor and shields aren’t going to last you throughout an entire 5E campaign. It is important to use spells, magical items, feats, and class features to keep your AC high throughout the campaign. This is especially important if you plan on being on the frontlines and distracting enemies.

Another way to improve your chances of not getting hit involve giving enemies disadvantage on attack rolls. This is much more common than buffing your own AC, but will not be the focus of this guide.

Spells for buffing AC in DnD

Magic is the first method of improving AC in 5E. If you want high AC early, consider the Cleric, Sorcerer, and Wizard spell lists. Shield provides a massive +5 to AC that lasts a turn, while Shield of Faith provides a +2 which lasts for 10 minutes. That’s up to 100 rounds, since 10 rounds are in a minute.

While there are a handful of spells that will improve AC, handy ones include:

  • Barkskin, which sets AC to 16 if it would be lower.
  • Haste, which adds two to AC while providing bonuses to speed and number of actions per turn.
  • Mage Armor, which sets AC to 13 plus Dexterity modifier.
  • Warding Bond, which improves a target’s AC and saving throws by one, as well as giving it resistance to all damage. However, you take the same amount of damage.

Items that buff AC in DnD

Magical gear and spells provide gigantic boosts to AC that allow a character to survive the mid and late game of 5E.

The most prevalent bonus you will receive are +1, +2, and +3 Armors. These magical items add flat bonuses on top of whatever AC the armor would normally add. For example, Leather Armor normally has an AC of 11 plus Dexterity modifier. A +3 Leather Armor would have 14 plus Dexterity modifier instead. Same rules apply for shields; a +3 Shield adds five to AC, instead of two.

Several magic items, such as the Ring of Protection, provide bonuses to AC that are not worn as armor. If you attune to these items, or wear ones that don’t require attunement, you gain those bonuses to AC. They stack with each other and with any bonuses for armor. These magical items are plentiful. You are likely to run into several over the course of your journey, with some of them giving more situational or interesting defensive abilities than bonuses to AC.

For example, Lae’zel from the above example gets +1 Plate Mail, a +1 Shield, and a Ring of Protection. All of those bonuses add together. So, the calculation is 19 plus three plus one, for a total of 23.

Feats that increase AC in DnD

Precious few feats actively improve AC. A +2 to Dexterity as an ability score improvement is a tried-and-true method to boost your defensive stat, but several feats have the opportunity to boost your AC situationally. They include:

  • Defensive Duelist, to add Proficiency to AC as a reaction to a melee attack, but only while wielding a finesse weapon.
  • Dragon Hide sets your AC to 13 plus Dexterity modifier, but only for Dragonborn.
  • Dual Wielder gives a +1 to AC while dual wielding weapons.
  • Gift of the Metallic Dragon allows you to give a target a bonus to AC equal to your proficiency modifier as a reaction.
  • Getting proficiency in armor or shields through feats (or multiclassing) can allow you to equip new items and achieve a higher AC without penalties.

Related: How to multiclass in Baldur’s Gate 3

Class Features that improve AC in DnD

The most prevalent examples of class features that directly improve AC are the Defense Fighting Style available to Fighters, Rangers, and Paladins, as well as Forge Domain Clerics. These class benefits grant a flat +1 to AC while wearing armor. These bonuses can stack with one another, if you want them to. But, you can only select the Defense Fighting Style once. So, a Fighter 1/Paladin 2 can’t take the Defense Style twice.

That isn’t all, though. Some classes replace the default 10 to AC by adding a flat bonus to it. Draconic Sorcerers, for instance, set their AC to 13 plus Dexterity modifier instead of 10. Barbarians, while unarmored, use the calculation of 10 plus Constitution modifier plus Dexterity modifier. Similarly, Monks use 10 plus Wisdom modifier plus Dexterity modifier when they are not wearing armor.

Some classes can provide magical bonuses to armor, allowing you to boost AC until you find magic armor. The Artificer’s Infusion mechanic can let the Artificer improve the AC of nonmagical armor by plus-one. Similarly, a Forge Cleric can temporarily cause nonmagical armor to grant a plus-one.

How to debuff enemy AC in DnD

The Oathbreaker Paladin grants his blessing to a new Oathbreaker in Baldur's Gate 3.
Weakening a target’s AC is tough, but there are work-arounds. Screenshot by Dot Esports via Larian Studios.

It is very irregular to debuff an enemy’s numerical AC in 5E. There are very few effects that actively do so. It is more typical for spells and effects to grant you advantage when making attack rolls against a target.

The Slow spell will allow you to lower a target’s AC by two for the duration of the spell. But there are actually no other official spells that will allow you to reduce AC. There are also no subclasses that focus on reducing the armor class of your opponent.

This is because 5E focuses a lot more on the advantage system, rather than hard number increases or decreases. And if you’re looking for ways to get advantage on attack rolls, then boy do we have good news for you.

  • You can gain advantage on targets that are having trouble seeing you, such as from Blindness, as well as using the hide action.
  • Targets that are prone take attacks from melee range with advantage.
  • Some spells grant advantage to attacks. Guiding Bolt, for example, grants the next attack on a target advantage.
  • Many classes and subclasses offer ways to get advantage on attacks, either through granting it straight-up or applying making it easier to apply the condition.
    • The Oath of Vengeance Paladin, for example, may use their Channel Divinity to gain advantage on all attack rolls against a target until it goes down.
    • The Assassin Rogue has advantage on attacks against creatures that haven’t moved in combat.
    • The Monk can use their Stunning Strike feature to potentially stun a target. Attacks against stunned creatures have advantage.

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Jason Toro-McCue
Contributing writer and member of the RPG beat. Professional writer of five years for sites and apps, including Nerds + Scoundrels and BigBrain. D&D and TTRPG fanatic, perpetual Fighter main in every game he plays.