Mechanic Overview: Armor Class 5e

What is Armor Class?

In 5th Edition, Armor Class (AC) is one of the most important aspects of any character because it determines how easily they can be hit. While it is specifically called “armor” class, a creature’s AC does not always entirely depend on how much armor a creature is wearing. A high AC can mean that a creature is particularly dexterous or that they can use magic to defend themselves.

There are a number of things that can increase a character’s AC, a few of which being armor, magic items, class features, and racial traits. In this Mechanic Overview, we will be covering the basics of AC, and how it interacts with other aspects of D&D’s 5th Edition.

How does AC work in 5e?

When making an attack against a creature, if the attacker meets the defender’s AC the attack will hit. When making a Saving Throw, Armor Class does not affect the outcome of the roll.

How do you calculate Armor Class in 5e?

When unarmored, your base Armor Class is 10 + Dexterity modifier. If you have a spell, item, feat, or racial trait that affects your Armor Class then the calculation will change. 

The two most common ways to increase AC are to pump your Dexterity modifier (if you’re not wearing heavy armor) or to equip better armor. Below are some examples of different ways to increase AC, these options focus mainly on the Basic Rules, though some examples are given from other sources

How to increase your Armor Class

Armor

Armor is one of the most common ways to increase Armor Class in 5e. A character’s ability to wear armor directly ties to the class they take, though their ability scores and any feats they have also come into play.

Below is a table of the different types of non-magical armor that can be found in D&D 5e, before choosing to wear a certain type of armor, make sure that your class has proficiency in it, and that you meet any other requirements such as the minimum STR requirement for Heavy Armor and only being able to equip non-metal armor for Druids.

Class Features

Some classes gain the ability to increase their base AC:

• Monk: Unarmored Defense – Base AC = 10 + your Dexterity modifier + your Wisdom modifier
• Barbarian: Unarmored Defense – Base AC = 10 + your Dexterity modifier + your Constitution modifier
• Artificer Infusion: Enhanced Defense – This infusion allows you to increase the AC of a shield or suit of armor by 1. At 10th level, this bonus becomes +2.
• Fighter: Defense Fighting Style – +1 while armored.

There are other subclasses that can boost AC because of class features:

• Forge Domain Cleric: Soul of the Forge – Gain a +1 bonus to AC when wearing heavy armor.
• Bladesinging Wizard: Bladesong – Add your INT modifier to AC

Magic Items

While magic items are rare and expensive, there are quite a few that can boost your AC. Some examples are below:

• Armor +X – +1/2/3 AC
• Arrow-Catching Shield – +2 AC against ranged attacks, among other effects
• Cloak of Protection – +1 AC and to all saving throws
• Demon Armor – +1 AC, among other effects 
• Dragon Scale Mail – +1 AC, among other effects
• Dwarven Plate – +2 AC, among other effects
• Elven Chain – +1 AC, among other effects
• Glamoured Studded Leather – +1 AC, among other effects
• Ioun Stone (Protection) – +1 AC
• Ring of Protection – +1 AC and to all saving throws
• Shield +1/2/3 – +3/4/5 AC (because shields grant +2 AC, the +1 shield will grant +3 AC and so on)
• Staff of Power – +2 AC and to all saving throws, among other effects

Racial Traits

Not many races give an inherent bonus to AC because of how strong an AC bonus at 1st-level tends to be. Some races that were introduced outside of the core sources that boost AC are:

• Tortle: Natural Armor – Base AC increases to 17 and can use Shell Defense to gain +4 to AC, among other effects.
• Warforged: Integrated Protection: – +1 AC

Feats

We wrote an entire article on 5e feats so if you are looking for an in-depth look at them, that is where you can find it. Below are the feats that directly and indirectly impact AC:

• Defensive Duelist – You can use your reaction to add your proficiency bonus to your AC
• Dragon Hide – Base AC is 13 + your Dexterity modifier
• Dual Wielder – +1 while wielding two weapons
• Heavily Armored – Gain proficiency with heavy armor
• Lightly Armored – Gain proficiency with light armor
• Medium Armor Master – Add 3, rather than 2, to your AC if you have a Dexterity of 16 or higher.
• Moderately Armored – Gain proficiency with medium armor and shields
• Shield Master – You can add your shield’s AC bonus to any Dexterity saving throw you make against a spell or other harmful effect that targets only you

Spells

Because of the nature of the D&D 5e system, a lot of spells result in providing advantage or disadvantage to attacks, or resistance to a certain damage type. That said, there are a number of spells that can help with raising AC. Though none of these are permanent, some last longer than others:

• Barkskin: 1-hour duration – AC can’t be less than 16
• Ceremony (Wedding): 7 days duration – +2 AC while both creatures are within 30ft of each other
• Haste: 1-minute duration – +2 to AC, among other effects
• Mage Armor: 8-hour duration – Base AC becomes 13 + Dexterity Modifier
• Polymorph/True Polymorph: 1-hour duration – Creature adapts the AC of the creature it was turned into 
• Shield of Faith: 10-minute duration – +2 to AC
• Tasha’s Otherworldly Guise: 1-minute duration – +2 AC, among other effects
• Warding Bond: 1-hour duration – +1 AC, among other effects
• Shield: 1 round – raises your AC by 5 until the end of the round. Can be used as a reaction when you’re hit with an attack.

Cover

One of the easiest ways to increase your armor class that is commonly overlooked is by using cover. Using the environment to your advantage grants the bonuses listed below:

• Half cover: +2 AC – A target has half cover if an obstacle blocks at least half of its body. The obstacle might be a low wall, a large piece of furniture, a narrow tree trunk, or a creature, whether that creature is an enemy or a friend.
• Three-quarters cover: +5 AC – A target has three-quarters cover if about three-quarters of it is covered by an obstacle. The obstacle might be a portcullis, an arrow slit, or a thick tree trunk.
• Total cover – Can’t be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect. A target has total cover if it is completely concealed by an obstacle.

Why doesn’t AC automatically increase with levels?

AC in D&D 5e doesn’t increase much above the low 20s and can be reached by PCs and NPCs at low levels. For example, a 1st-level Paladin wearing plate mail and wielding a shield has an AC of 20. An Adult Black Dragon, which is a challenge rating 17, only has an AC of 19. What gives?

D&D 5e is built around a system called “Bounded Accuracy” which locks “target numbers” in the game, such as Armor Class and the Difficulty Class, to levels that are reasonable to achieve at any level.

Under bounded accuracy, you won’t see these targets increase above a certain ceiling as characters progress. Instead, these targets remain fairly static, only ever reaching between 20 and 30. 

“But” you may ask, “as characters level up, they face threats that have a higher chance to hit and can do more damage. Won’t that mean that characters facing these threats will die easier?” 

Well, as characters level up, they are provided more tools that will allow them to deal with higher-level threats. These tools usually come in the form of a larger pool of hit points, more damage per round, or various other abilities they can use to swing the encounter in their favor.

Bounded accuracy suggests that there shouldn’t be a minimum level where you could ever hope to hit an Adult Black Dragon. Because an Adult Black Dragon’s AC is 19, they could be hit by a 1st-level character with a +5 to hit about 25% of the time.

Now, whether or not it’s reasonable for a party of 1st-level adventures to be able to defeat an Adult Black Dragon is another matter. While a party of new adventurers would likely fair poorly against such a great threat, if the PCs could rally a city against this dragon, or put it at a severe disadvantage, they actually may have a shot to kill it. 

In short, Bounded Accuracy allows for a number of things, mainly:

• When characters level up, they actually get better at things. When you get +1 to an ability, you actually get 5% better at performing tasks in that area. In a system without Bounded Accuracy, these increases are necessary to provide even a basic level of competence to complete certain tasks.
• PCs that aren’t specialized in a certain field can still participate. A Barbarian with an 8 in Charisma can still be reasonably effective in social situations, even if they have a -1 modifier.
• It provides a consistent difficulty level for tasks. This allows DMs to improvise more effectively because they know that breaking down an iron door is a DC 17 Strength check, no matter what level the characters are.
• It expands the list of encounter options over time, it doesn’t limit them. Because the character’s AC doesn’t increase above levels that can be met by lower-level creatures, the pool of viable enemies that the party can face only expands over time.

Conclusion

In short, AC is a simple enough mechanic on the surface. It allows new players to hop into the game easily, by telling them “if you hit this number, that creature takes damage”. But, when combined with the other mechanics in the 5e system, such as Advantage and Disadvantage, it still provides enough complexity and depth to be relevant to higher levels of play.

If you enjoyed our overview of the AC mechanic or would like to see other mechanics dissected in future posts leave us a comment below! Thanks for reading and remember, in the immortal words of Wayne Gretzky Michael Scott, “you miss 100% of the shots you don’t take”. 

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Mike Bernier

Mike Bernier is the lead content writer and founder of Arcane Eye. He is a Adamantine best-selling author of Strixhaven: A Syllabus of Sorcery on DMs Guild and is a contributing author at D&D Beyond. Follow Mike on Twitter.