Armor Class in D&D 5e: How AC Actually Works

Armor Class is the number enemies need to roll (on a d20 + their attack modifier) to hit you. Higher AC = harder to hit.

This guide covers how AC is calculated, which classes get what, and why a few more AC points matter more than you think.

The Core Formula

At the simplest:

AC = Your armor's base + Your Dex modifier (up to the armor's limit) + Shield bonus + magical bonuses

Armor types have different limits on Dex bonus.

Armor Types

No Armor

Base AC = 10 + your Dex modifier. No limit.

A 16 Dex character has AC 13 unarmored. A 20 Dex character has AC 15.

Light Armor

Add your full Dex modifier.

• Padded: AC 11 + Dex. Disadvantage on Stealth.
• Leather: AC 11 + Dex.
• Studded Leather: AC 12 + Dex.

A 16 Dex character in Studded Leather: AC 15.

Medium Armor

Add your Dex modifier, max +2.

• Hide: AC 12 + Dex (max 2).
• Chain Shirt: AC 13 + Dex (max 2). No Stealth disadvantage.
• Scale Mail: AC 14 + Dex (max 2). Disadvantage on Stealth.
• Breastplate: AC 14 + Dex (max 2). No Stealth disadvantage.
• Half Plate: AC 15 + Dex (max 2). Disadvantage on Stealth.

A 14 Dex character in Half Plate: AC 17. A 20 Dex character in Half Plate: still AC 17 (capped).

Heavy Armor

No Dex modifier. Need Strength score to wear without speed penalty.

• Ring Mail: AC 14. Str 13.
• Chain Mail: AC 16. Str 13.
• Splint: AC 17. Str 15.
• Plate: AC 18. Str 15.

Plate + shield = AC 20, no Dex needed.

Shields

+2 AC. Can be wielded with most one-handed weapons. Can't be used with two-handed weapons.

A Fighter with Plate (AC 18) + Shield = AC 20.

Unarmored Defense

Some classes get Unarmored Defense:

• Barbarian: AC = 10 + Dex mod + Con mod.
• Monk: AC = 10 + Dex mod + Wis mod.

With high Con/Wis, these classes can reach AC 18-20 without wearing armor.

A level 5 Barbarian with 16 Dex + 16 Con: AC 16 + shield = 18.

A level 5 Monk with 16 Dex + 16 Wis: AC 16 (can't use shield with Unarmored Defense).

Bracers of Defense

Unarmed, no shield. +2 AC.

This can stack with Unarmored Defense for Monks and Barbarians.

Magical Armor

+1, +2, or +3 armor adds to the base AC. Magical armor is rare but impactful.

Why AC Matters

Every point of AC is roughly 5% fewer hits. Raising AC from 15 to 20 (a 25% reduction in hits) reduces incoming damage by roughly 25% over time.

In solo play, reducing incoming damage is survival. Fewer hits = fewer HP losses = fewer healing resources needed = more time in the fight.

AC Targets

• 10-12: Typical unarmored caster. Fragile.
• 13-15: Light armor, medium armor without max Dex. Fine for back-line casters.
• 16-18: Standard for martial classes. Half Plate + 14 Dex, or Plate alone.
• 18-20: Target for tanks. Plate + Shield. 2x Uncanny Dodge or Barbarian Rage effectively doubles this durability.
• 21-23: Very high. Usually requires magic items or class features (Bladesinger spells, Forge Cleric aura, Shield spell reactively).

Ways to Boost AC

• Better armor. Upgrade from Leather to Plate if you can wear it.
• Shield. +2 AC, no real downside if you have a free hand.
• Raise Dexterity. Only if you're in light or medium armor.
• Unarmored Defense. Monk or Barbarian.
• Spells.
  • Shield (reaction): +5 AC until next turn. Insane.
  • Mage Armor: 13 + Dex, for 8 hours, non-concentration.
  • Shield of Faith: +2 AC, concentration.
  • Mirror Image: Effectively higher AC via duplicates.
• Magic items. Ring of Protection +1, Cloak of Protection +1, magical armor.
• Fighting Style (Defense). +1 AC. Fighter, Paladin, Ranger, some others.

Common Misconceptions

"Dex is the only stat that matters for AC." Not if you wear heavy armor or use Unarmored Defense. Con, Wis, Strength can matter.

"Shield always gives +2." Only when wielded. You need to lift and ready it.

"I can wear plate as a Wizard." No. Plate requires Strength 15. Also, you need the proficiency.

"Mage Armor is concentration." No. Mage Armor lasts 8 hours without concentration. One of the best 1st-level spells for Wizards and Sorcerers.

"Shield spell stacks with itself." No. Shield is a reaction, cast once per trigger. It provides +5 AC until next turn, already huge.

The Endlessness and AC

Our AI Dungeon Master calculates AC automatically based on your armor, Dex, class features (Unarmored Defense), shields, magic items, and active spells. When you cast Shield, the +5 applies until your next turn. When you cast Mage Armor, it lasts 8 hours.

For related reads, our combat rules guide and character creation guide cover how AC plays into broader character design.

Final Takeaway

Higher AC is survival. Get your AC to 18 or above at low levels. Get to 20 by level 5. Stay defensive. Drink your AC-boosting potions before boss fights.

Try different AC builds on The Endlessness and see how much defense matters.