5e Armor Class Calculator Online

This 5e Armor Class (AC) Calculator lets you enter your ability modifiers, pick armor or an unarmored formula, add a shield and magic bonuses, and apply spell or situational effects. It shows your current AC and, optionally, the AC “vs this attack” when you toggle things like cover or the Shield spell. A breakdown explains every step so you can verify the math at the table.

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How to use the tool

1. Enter ability modifiers (Dex, Con, Wis). Use your character sheet values.
2. Select armor or leave “No armor.” The tool enforces light/medium/heavy rules for Dexterity.
3. Choose shield if carried. Add shield enhancement if magical.
4. If unarmored, pick the base formula (e.g., Barbarian or Monk Unarmored Defense, Draconic Resilience, natural armor, or Mage Armor).
5. Toggle effects like Barkskin (AC floor 16), Haste (+2), Warding Bond (+1). Use “Other bonuses” for items like Rings/Cloaks of Protection or Bracers of Defense. Use “Custom modifier” for any table ruling or homebrew.
6. Pick cover if relevant to the current attack (+2 half cover, +5 three-quarters cover).
7. Use “Shield spell +5” when resolving a specific attack. The tool will show “AC vs this attack.”
8. Read the breakdown to see the base formula, added bonuses, floors, and situational modifiers.

What AC measures

AC represents how hard you are to hit with an attack. Attacks roll a d20 + attack bonus. If the result meets or exceeds your AC, the attack hits. Higher AC reduces hit chance.

Base AC sources (pick exactly one)

• Armor
  • Light armor: Base AC shown by the armor + your full Dex modifier.
  • Medium armor: Base AC + Dex modifier capped at +2.
  • Heavy armor: Fixed AC. Dex does not apply.
• Unarmored formulas (no armor worn)
  • Default: 10 + Dex.
  • Barbarian Unarmored Defense: 10 + Dex + Con. Shields allowed.
  • Monk Unarmored Defense: 10 + Dex + Wis. Shields not allowed.
  • Draconic Resilience: 13 + Dex. No armor.
  • Natural Armor: A fixed base (e.g., 17) with or without Dex, depending on the trait. Use the inputs to reflect your creature’s entry.
  • Mage Armor: 13 + Dex while not wearing armor. It replaces, rather than stacks with, other unarmored bases. Pick whichever base gives the highest legal result.

Armor, shields, and magic bonuses

• Armor enhancement (+1 to +3): Adds directly to AC when you are wearing that armor.
• Shield: +2 AC when equipped and allowed by your base. A magic shield adds its enhancement on top of the +2.
• Defense Fighting Style: +1 AC while wearing armor (not unarmored).
• Dual Wielder feat: +1 AC while wielding two melee weapons. If you use this, enter +1 in “Other bonuses.”
• Other bonuses: Generic field for items like a Ring or Cloak of Protection (+1), Bracers of Defense (+2, only if not wearing armor or a shield), or similar features that give flat AC bonuses.

Spells and feature effects

• Mage Armor: Sets base AC to 13 + Dex while unarmored. Do not stack it with other base formulas; use the best legal base.
• Barkskin: AC cannot be lower than 16 after all base and legal stacking are considered. It is a floor, not a bonus.
• Haste: +2 AC.
• Warding Bond: +1 AC to the bonded creature.
• Shield spell: +5 AC until the start of your next turn. It’s reactive to a specific attack. Use the checkbox to preview the temporary AC for that attack.

Cover and situational modifiers

• Half cover: +2 AC vs the attack in question.
• Three-quarters cover: +5 AC vs the attack in question.
• Full cover: not targetable; the tool does not add an AC number for this case.
• Custom modifier: Use this for table rulings, rare features, or temporary effects not listed elsewhere.

Calculation order the tool follows

1. Choose the base AC:
   • If wearing armor: use that armor’s base and Dex rules (light full Dex, medium cap +2, heavy no Dex).
   • If unarmored: compare the eligible formulas (e.g., 10+Dex, Barbarian, Monk, Draconic, Natural Armor, Mage Armor) and use the highest legal base.
2. Apply floors like Barkskin (raise to 16 if lower).
3. Add static bonuses:
   • Shield (+2) and shield enhancement if allowed by the chosen base.
   • Armor enhancement if wearing armor.
   • Defense style (+1) only while wearing armor.
   • Haste (+2), Warding Bond (+1), Other bonuses, Custom modifier.
4. Situational layer:
   • Cover bonus (+2 or +5) and the Shield spell (+5) are shown in the “AC vs this attack” line so you can compare your normal AC and your per-attack AC.

Rules interactions the tool enforces

• Medium armor caps Dex bonus at +2.
• Heavy armor ignores Dex.
• Wearing armor disables Monk/Barbarian Unarmored Defense and Mage Armor.
• Monk Unarmored Defense does not allow shields.
• Barbarian Unarmored Defense allows shields.
• Mage Armor is a replacement base, not a stacking bonus. Pick the best legal base.
• Barkskin is a floor at 16, not a bonus that stacks on top.
• Defense Fighting Style only applies while you are wearing armor.

Common examples

• Chain mail + shield + Defense style: 16 (chain) + 2 (shield) + 1 (style) = 19.
• Wizard with Mage Armor and Dex +3: 13 + 3 = 16; with the Shield spell for one attack: 21.
• Barbarian UD Dex +2 Con +3 with shield: 10 + 2 + 3 + 2 = 17.
• Monk UD Dex +3 Wis +3, Bracers of Defense +2: 10 + 3 + 3 + 2 = 18 (no armor or shield).
• Barkskin check: If your computed AC is 14, Barkskin raises it to 16.

Troubleshooting and tips

• If two options seem to stack, check whether one is a base and the other is a bonus. Bases don’t stack; the highest legal base wins.
• Use “Other bonuses” for static, always-on items that grant flat AC bonuses. Use “Custom modifier” for anything unusual.
• Keep “Shield spell +5” off until you are resolving an attack. Then toggle it to see your reactive AC for that attack.
• Cover only matters relative to a specific attacker. Use it in “AC vs this attack,” not in your always-on AC.

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