How armour class works in D&D 5e

Learn how armour class works and how to improve your AC

Armour class (or AC) is one of the fundamental stats associated with any character, creature and even plant in D&D. It’s one of the more crucial elements of your character but don’t worry, we’re here to explain what it is, how it works and how to maximise your AC to make the most of your character.

What is armour class?

Armour class is used in D&D 5e to determine how difficult a character or creature is to hit with an attack. It can represent lots of different forms of preventing being damaged by an attack from wearing armour to deflect hits, naturally tough skin, a character’s speed and ability to dodge as well as magical protections a character might have.

Armour class is represented by a number. When an attacker rolls to hit a defender, they must roll a score equal to or higher than the defender’s armour class. If they do this, the roll is considered a hit, if the score is lower, then the roll is considered a miss.

How to calculate your character’s armour class

At its most basic level, armour class is calculated as 10 + your character’s dexterity modifier. So if your character has a dexterity of 16, they will have a dexterity modifier of +3 meaning they’ll have an armour class of 13.

You’re not just limited by your dexterity though. Wearing armour is the most common way to improve your armour class further and can compensate nicely for characters with a low dexterity score. In addition, racial traits, magic items and spells can all be employed to improve your armour class. Below we’ve detailed how some of these additional methods work to boost your AC.

How to improve your armour class

Armour

Armourer

Armour is the most obvious way to improve your armour class. As you’d expect, it involves donning some protective clothing to deflect attacks that may get through your natural dodging and parries. Armour improves your AC by improving your base AC at which armour class is calculated. For instance, if your character is wearing studded leather armour, they calculate their AC based on 12 + their dexterity modifier rather than the usual 10 when unarmoured.

Light armour like studded leather works really well for characters with a lot of dexterity as it enhances your natural, agile defences. Some characters may be less built to defend themselves, in which case, they may choose to wear medum or heavy armour. This usually increases your base AC, but often means you can only benefit from your dexterity modifier in a limited way (or not at all) due to the restricted movement. For example, a character wearing half plate will have an AC of 15 + their dexterity modifier but with a maximum of +2 to that value.

Heavy armour will negate the impact of dexterity entirely from your armour class, but with the benefit of a higher base AC. For example, plate armour provides a flat AC of 18. Just remember that you’ll need to be proficient in an armour type to gain the benefits of wearing it. Some armour types will also make it harder to perform stealth actions or might be so heavy, they require a certain strength to wear effectively.

Below you can see all standard forms of armour and the armour class provided by that armour:

ArmourTypeCostArmour ClassStrength ModifierStealthWeight
PaddedLight Armour5gp11 + Dex ModifierN/ADisadvantage8 lb
LeatherLight Armour10gp11 + Dex ModifierN/AN/A10 lb
Studded LeatherLight Armour45gp12 + Dex ModifierN/AN/A13 lb
HideMedium Armour10gp12 + Dex Modifier (Max +2)N/AN/A12 lb
Chain ShirtMedium Armour50gp13 + Dex Modifier (Max +2)N/AN/A20 lb
Scale mailMedium Armour50gp14 + Dex Modifier (Max +2)N/ADisadvantage45 lb
Breast PlateMedium Armour400gp14 + Dex Modifier (Max +2)N/AN/A20 lb
Half PlateMedium Armour750gp15 + Dex Modifier (Max +2)N/ADisadvantage40 lb
Ring MailHeavy Armour30gp14N/ADisadvantage40 lb
Chain MailHeavy Armour75gp16Str 13Disadvantage55 lb
SplintHeavy Armour200gp17Str 15Disadvantage60 lb
PlateHeavy Armour1500gp18Str 15Disadvantage65 lb

Shields

Mountain Dwarf

Shields operate a little differently from armour. A character can wield a single shield (so no double shields like Captain America I’m afraid… Well, you could but you’d only gain the benefit of the one shield and could only use the second shield as an improvised weapon so not the most effective approach). A standard shield will give you +2 to whatever your armour class so is a great way to boost your AC. The only drawback is that your hand can’t now be used for something else like wielding a 2 handed-weapon, dual wielding weapons or for spellcasting.

Racial Traits

A handful of races have a natural hardiness that increases their AC naturally. Such features are rare for races as an AC bonus at level 1 can be a powerful bonus and make you extremely difficult to hit if optimised right. Those races are:

Tortles – Tortles have a naturally tough shell that also makes wearing armour extremely difficult. Tortles have a base AC of 17 that is unaffected by dexterity modifiers. They also can’t gain the benefits of wearing armour (though can benefit from using a shield).

In addition, they can retreat into their shell for an extra +4 AC but are very limited in what they can do in this position.

Warforged – Warforged have a +1 to their AC.

Class Features

Some classes have traits that allow them to increase their armour class. Perhaps it’s due to being extremely hardy or due to training in a certain technique. These classes are:

Artificer – Artificers love to tinker with things to improve their functionality, this includes enhancing armour with infusions. Their infusions allow them to grant a +1 bonus to the AC granted by armour or a shield which increases to +2 when they reach level 10.

Barbarian – Barbarians are warriors specialised in being very tanky and can both deal and take a lot of damage. Their unarmoured defence trait means they can also add their constitution modifier to their AC meaning their AC is calculated as:

10 + dexterity modifier + constitution modifier

Fighter – Fighters are highly trained warriors that can train in certain fighting styles. One of these styles is the defence fighting style which adds +1 to a fighter’s AC while they’re wearing armour.

Monk – Monks are highly trained warriors that can weave in and out of opponents relying more on skill than armour to protect them. Their unarmoured defence allows them to add their wisdom modifier to their armour class meaning their AC is calculated as:

10 + dexterity modifier + wisdom modifier

A couple of subclasses also add bonuses to AC. These are:

Forge Domain Cleric – Their Soul of the Forge ability adds +1 to their AC when wearing heavy armour.

Bladesinging Wizard – Bladesingers use their bladesong ability to help them operate on the front lines of combat allowing them to add their intelligence modifier to their AC meaning their armour class is worked out as:

10 + dexterity modifier + intelligence modifier

Feats

Feats can be taken (if your DM allows them) in place of ability score improvements when levelling up. They represent unique traits that can provide skills not generally available to a particular class. Some of these feats can be used to improve your AC, these include:

  • Defensive duelist – You can use your reaction to add your proficiency bonus to your AC
  • Dragon Hide – Your base AC is 13 + your dexterity modifier
  • Duel Wielder – Gain +1 to AC when duel wielding
  • Heavily Armoured – Gain proficiency with heavy armour
  • Lightly Armoured – Gain proficiency with light armour
  • Medium Armour Master – Your dexterity modifier when wearing medium armour can be a maximum of +3 instead of +2
  • Moderately Armoured – Gain proficiency with medium armour and shields

Spells

Wizard casting spells

A lot of spells can be used to provide various buffs to a character and a few of these can be used to increase a character’s armour class. This can be particularly useful if you’re a spellcaster like a wizard with few other defences or if you are well-armoured, but thrown so much into the thick of combat that you may need some extra protection as can be the case with a paladin. It should be noted though, that these spells only provide temporary enhancements to AC that can last as little as a turn.

These AC enhancing spells include:

  • Barkskin – AC is at least 16
  • Ceremony (Wedding) – +2 AC while both creatures are within 30ft of each other
  • Haste – +2 AC along with other bonuses
  • Mage Armor – Base AC becomes 13 + Dexterity Modifier
  • Polymorph/True Polymorph – Creature gains the AC of the creature it was turned into 
  • Shield – Reaction that increases AC by 5 for a round
  • Shield of Faith – +2 AC
  • Tasha’s Otherworldly Guise – +2 AC along with other benefits
  • Warding Bond – +1 AC along with other benefits

Magic Items

Magic items are powerful and more rare than other standard items you might acquire. There’s no guarantee that your DM will bestow an AC increasing item upon your party but they are there and available in the game if included by your DM. Often, these magic items might include enhanced sets of armour that provide additional bonuses to AC or robes, rings and amulets imbued with powerful magic to protect its wearer.

You can find details of armour class enhancing magic items in the Dungeon Master’s Guide.

Cover

Cover is easily forgotten about as a way to enhance AC, particularly because it’s highly situational and can’t be relied on, but different types of cover provide varying levels of AC bonus. It might be a low wall, some battlements, a tree or even the dead husk of some huge creature. Below, we’ve detailed the types of cover and the AC bonus provided by it:

Half Cover (+2 AC) – Half cover involves anything that covers about half your body and might include furniture, low walls, battlements and even another creature.

Three-Quarters Cover (+5 AC) – This involves anything that covers about three quarters of your body which might include arrow slits in a keep, a large tree trunk or a wagon.

Total Cover – If you’re in total cover and are entirely obscured from view, you can’t be targeted in the conventional sense. It is possible though that an area of effect spell might still hit you under these circumstances and if cast in the right place.

In the case of cover, it is for your DM to determine how well a piece of cover protects your character.

Best character builds for high armour class

Warforged

This is a tricky question and depends on what your DM is willing to allow. Some of the craziest high armour class builds rely on magic items, spells and some very hefty multiclassing to stack benefits that I imagine most DMs wouldn’t allow at their table.

For the purposes of this question, we’ll work with a few assumptions. First is we won’t be stacking unarmoured defence benefits of different classes as this goes against the spirit of the game. We also will assume that you have no magic items to benefit from as there’s no guarantee you will have a DM generous enough to bestow a multitude of armour class enhancing gear on you (or a party willing to let you take all the loot to make you near indestructible). Finally, spells are temporary and again, to fully max out your AC, you’d be reliant on casting spells over a period of time rather than actually fighting.

With those ground rules out of the way, here’s some of the highest AC builds available in D&D 5e:

Paladin or fighter – Paladins and fighters can both use heavy armour so you’ll want to equip plate mail and a shield for an AC of 20. You’ll then need to take the defence fighting style which will bring your AC up to 21. If you choose to play as a warforged, this will increase your AC a little more up to 22. We won’t include it in this calculation, but paladins can have access to the shield spell which it’s worth bearing in mind will increase your AC by +5 for a turn as a reaction.

Barbarians and Monks – Barbarians and Monks have a feature called unarmoured defence which allows them to add their dexterity modifier and either their constitution or wisdom modifier to their AC. If you can achieve +5 to both these modifiers, this gets you to an AC of 20 without armour. A warforged will give you +1 bringing you up to 21 however, the tortle is probably a better option here as you get a base AC of 17 (though can’t add your dexterity modifier to this). This would still get you to 22 AC with a +5 in wisdom or constitution.

An even better option would be to take the dragon hide feat which sets your base AC to 13 and you can benefit from both your dexterity and wisdom or constitution modifiers getting you up to an AC of 23. You could also take a shield if you’re a barbarian for an AC of 25. While the monk can’t take a shield, they can take the dual wielder feat, have 2 weapons and get a +1 to their AC taking you up to 24. For an even bigger bonus, you can even take the defensive duelist feat which will allow you to add your proficiency bonus to your AC as a reaction. This means a potential for +6 to your AC but can only be taken against one attack per turn but does mean a potential AC of 30 on a reasonably regular basis!

Published by DM Ben

Ben is an experienced dungeon master and player who's been immersed in the D&D universe since he was a teenager over 20 years ago. When he's not writing for Dungeon Mister, Ben loves creating fiendish puzzles and devious dungeons for his players. He's an especially big fan of the Ravenloft and Dragonlance settings.

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