D&D 5e Armor Class Calculator
Pick your armor, enter Dexterity, and include bonuses like shield, cover, and magical gear.
How Armor Class Works in D&D 5e
Armor Class (AC) is the target number enemies must meet or beat on an attack roll to hit you. Higher AC means fewer successful enemy hits over time, which has a huge impact on survivability. In most cases, AC starts from your armor (or from being unarmored), then adds modifiers from Dexterity, shields, magical bonuses, class features, and sometimes cover.
This AC DnD calculator focuses on the core 5e rules and gives you a clean breakdown so you can quickly check if your build is using the right formula.
AC Formula Reference (Quick Version)
1) Unarmored
Default AC is 10 + Dexterity modifier, unless a class feature replaces it (for example, Monk or Barbarian formulas).
2) Light Armor
Light armor lets you add your full Dexterity modifier. Example: Studded Leather = 12 + Dex mod.
3) Medium Armor
Medium armor usually caps your Dexterity bonus at +2. If you have Medium Armor Master, that cap becomes +3.
4) Heavy Armor
Heavy armor ignores Dexterity for AC calculations. You use its fixed base value (for example, Plate = 18).
5) Shield and Other Bonuses
- Shield: +2 AC
- Magic armor or shield: item bonus applies
- Defense Fighting Style: +1 AC while wearing armor
- Cover: situational bonus (+2 or +5)
Why an AC DnD Calculator Helps
Character sheets often collect many temporary and permanent modifiers. A calculator helps you avoid common mistakes like double-counting Dexterity, forgetting heavy armor ignores Dex, or applying Defense style while unarmored. It is especially useful between levels when gear and feats change rapidly.
Example Build Walkthrough
Suppose your character has Dexterity 16 (modifier +3), wears Half Plate (15 + Dex max +2), carries a shield, and has +1 magic armor. Your AC would be:
- Half Plate base: 15
- Dexterity bonus in medium armor: +2 (capped from +3)
- Shield: +2
- Magic armor: +1
- Total: 20 AC
If you also had half cover from terrain, that becomes 22 AC against attacks affected by cover.
Common AC Mistakes to Avoid
- Adding Dexterity to heavy armor AC.
- Using full Dex with medium armor without the proper feat.
- Applying Defense Fighting Style while not wearing armor.
- Forgetting temporary effects (cover, spells, class reactions).
- Stacking formulas that do not stack (for example, two alternate base AC calculations).
AC Optimization Tips for Practical Play
Balance AC with Hit Points and Saves
AC is powerful, but it does not stop saving throw effects. A balanced defense includes HP, resistances, and saving throw support.
Track Conditional AC Separately
Keep one number for normal AC and another for “with shield spell,” “with cover,” or “with reaction active.” This keeps combat turns fast and accurate.
Recalculate at Key Milestones
Re-run your AC any time you gain a feat, upgrade armor, swap fighting style, or increase Dexterity. Small upgrades can significantly change your expected damage taken per encounter.
Final Notes
Use this calculator as a fast rules assistant during character creation and leveling. If your table uses homebrew or 2024 rules adjustments, treat the “Misc AC Bonus” field as a flexible slot for custom effects. For strict RAW decisions, always defer to your Dungeon Master.