D&D 5e Armor Class Calculator
Enter your character’s modifiers and equipment to calculate final AC. Use numeric modifiers only (for +3 enter 3, for -1 enter -1).
How Armor Class Works in 5e
Armor Class (AC) in Dungeons & Dragons 5e represents how difficult your character is to hit. When an enemy makes an attack roll, they compare that roll to your AC. If the roll equals or exceeds your AC, the attack hits. If it falls short, the attack misses.
Most characters calculate AC from one primary source (armor, mage armor, or unarmored defense), then add bonuses that can legally stack—like a shield, magic item bonuses, cover, or class features. The trick is that not everything stacks with everything else, which is why an AC calculator is useful.
Quick Rules for AC Stacking
- Choose one base AC formula: armor, no armor, mage armor, or unarmored defense.
- Shield usually adds +2 AC (plus any magic shield bonus).
- Magic armor bonus applies only when wearing armor.
- Defense fighting style works only while wearing armor.
- Cover bonuses are situational and not part of your always-on AC.
Common 5e AC Formulas
| Type | Formula | Notes |
|---|---|---|
| No Armor | 10 + Dex modifier | Default for most characters |
| Light Armor | Armor base + full Dex modifier | Leather/Studded Leather builds |
| Medium Armor | Armor base + Dex modifier (max +2) | Can still be penalized by negative Dex |
| Heavy Armor | Armor base only | Ignores Dex modifier entirely |
| Mage Armor | 13 + Dex modifier | Alternative formula, not worn armor |
| Monk Unarmored Defense | 10 + Dex + Wis | Requires no armor and no shield |
| Barbarian Unarmored Defense | 10 + Dex + Con | No armor, shield allowed |
Examples
Example 1: Fighter in Plate with Shield
Plate gives 18 AC. A shield adds +2. With the Defense fighting style (+1 while wearing armor), total AC is 21 before magic bonuses.
Example 2: Rogue in Studded Leather
Studded leather is 12 + Dex. If Dex modifier is +4, AC is 16. Add situational half cover and AC becomes 18 against ranged attacks from that position.
Example 3: Monk with High Dex and Wis
Monk unarmored defense uses 10 + Dex + Wis. A monk with Dex +4 and Wis +3 has 17 AC. A shield does not apply to this formula in normal play.
Tips to Improve AC Without Breaking Rules
- Increase your key ability scores (Dex for light armor, Wis for monk, Con for barbarian).
- Upgrade to better armor proficiency if your class allows it.
- Use shields when your build supports them.
- Pick defensive fighting styles and feats that match your class plan.
- Remember temporary buffs like shield of faith, haste, and cover in tactical positioning.
FAQ: AC Calculator 5e
Does AC include temporary spell effects?
Usually your “default AC” does not include temporary effects. This calculator includes a misc bonus and cover selector so you can test those situations quickly.
Do heavy armor users care about Dexterity modifier?
Not for AC calculation. Heavy armor ignores Dex modifiers entirely, both positive and negative.
Can I use mage armor and worn armor together?
No. You choose one base AC calculation method at a time. Mage armor is an alternative formula, not a stacking bonus on top of worn armor.
Why does my result show rules notes?
The calculator flags common rule interactions, like adding Defense style while not wearing armor, or entering magic armor bonuses with an unarmored formula.
Final Word
Use this AC calculator 5e tool as a quick build check before sessions, level-ups, and item upgrades. If your table uses house rules, you can still use the breakdown and adjust with the misc bonus field. Fast, clear AC math keeps combat moving and helps you make stronger tactical choices.