How Armor Class Works in D&D 5e (And How to Raise Yours)

26 March 2026

Picture combat without AC for a second: every sword swing would be a debate. Armor Class is the clean, impatient answer. An attack roll against you hits if it meets or exceeds your AC unless a feature says otherwise. It’s usually a stable number on your sheet unless you change gear, stance, magic, or position behind cover.

Two habits make AC click faster at real tables:

• AC cares about attack rolls, not about most saving-throw effects, many spells and breath weapons ask for saves, and your AC just watches from the bleachers.
• Cover can add to AC against ranged attacks (and many Dex saves), see cover when fights get ranged.

Unarmored baseline

Without armor or special features, your AC starts at:

10 + Dexterity modifier

Dex 16 (+3)? AC 13 in street clothes.

Light armor (full Dex, low base)

Light armor adds a base number + your full Dexterity modifier.

Stealth note: Padded imposes disadvantage on Dexterity (Stealth) checks.

Time at a glance (typical PHB timing): don 1 minute; doff 1 minute.

Medium armor (bigger base, Dex capped at +2)

Medium armor uses base + Dex modifier, but you can’t add more than +2 from Dex even if your Dex is higher.

So Dex 14 (+2) is “Breakpoint Avenue” for medium armor users who only care about AC.

Typical don/doff: 5 minutes to don; 1 hour to doff (bulkier harness than light).

Heavy armor (fixed AC, no Dex)

Heavy armor sets a fixed AC, don’t add your Dexterity to AC for that armor’s formula (unless a rule explicitly creates an exception elsewhere).

If you lack the Strength requirement, the armor reduces your speed by 10 (and you still need proficiency, see below).

Typical don/doff: 10 minutes to don; 1 hour to doff.

Shields (+2, but costs a hand)

A shield adds +2 to AC while you wield it. It usually costs one hand, which changes weapon math (no two-hander without dropping the shield story-wise).

Quick fantasy: plate + shield is AC 20 at baseline. A very sturdy mundane cap.

If you’re not proficient: don’t cosplay knight in stolen plate

If you wear armor you’re not proficient with, you have disadvantage on any ability check, saving throw, or attack roll that uses Strength or Dexterity, and you can’t cast spells.

That’s not “slightly worse”, that’s I shouldn’t be wearing this yet.

Who tends to wear what (class defaults, subclasses vary):

• Wizard / Sorcerer: no armor proficiency baked in → often Mage Armor, Shield, or positioning.
• Many sneaky/light martials: light (sometimes medium).
• Frontliners like Fighter / Paladin: often all armor + shields.

Class features that replace armor math (read your own entry)

Some characters stack differently:

• Barbarian Unarmored Defense: AC = 10 + Dex mod + Con mod while not wearing armor. You can use a shield with this feature.
• Monk Unarmored Defense: AC = 10 + Dex mod + Wis mod (no shield benefit with this feature).
• mage armor (spell): AC = 13 + Dex mod for the duration.

These don’t “stack” with armor’s formula. You pick the mode your feature says you’re using.

How you push AC upward without homebrew

• Better base armor (leather → studded; chain shirt → half plate) is the simplest early upgrade path.
• Shield if your kit allows, +2 is huge in bounded accuracy.
• Magic armor/shields (+1/+2/+3) and items like cloak/ring of protection (when your campaign awards them).
• Short-term spells such as shield (reaction +5 AC until your next turn) can swing a round, but they cost resources and triggers.

The defensive split you’ll feel past level 5

High AC answers swords and arrows and spell attacks. High saving modifiers answer dragon breath, charm, fear, knockdown, half-damage-on-a-save effects. You want both over a career; early on, not getting hit is the simplest story.

If you’re learning the parallel system, bookmark saving throws, it’s the other half of “why did that hurt me?”