D&D 5e Armor Class (AC) Calculator
Calculate your character’s Armor Class with all possible modifiers
Comprehensive Guide to Armor Class (AC) in Dungeons & Dragons 5th Edition
Armor Class (AC) is one of the most fundamental mechanics in Dungeons & Dragons 5th Edition, determining how difficult it is for enemies to land attacks on your character. Understanding how AC is calculated can mean the difference between a long, successful adventure and an early trip to the afterlife.
1. The Basic AC Formula
The most basic form of Armor Class in D&D 5e is calculated as:
AC = 10 + Dexterity Modifier
This represents an unarmored character with no special protections. Most creatures and characters will have additional modifiers that increase this base value.
2. Armor Types and Their AC Calculations
Different types of armor provide different levels of protection and modify your AC in various ways:
| Armor Type | AC Calculation | Dex Bonus Cap | Strength Requirement | Stealth Disadvantage |
|---|---|---|---|---|
| No Armor | 10 + Dex | None | None | No |
| Padded | 11 + Dex | None | None | Yes |
| Leather | 11 + Dex | None | None | No |
| Studded Leather | 12 + Dex | None | None | No |
| Hide | 12 + Dex (max 2) | +2 | None | No |
| Chain Shirt | 13 + Dex (max 2) | +2 | None | No |
| Scale Mail | 14 + Dex (max 2) | +2 | None | Yes |
| Breastplate | 14 + Dex (max 2) | +2 | None | No |
| Half Plate | 15 + Dex (max 2) | +2 | None | Yes |
| Ring Mail | 14 | None | None | Yes |
| Chain Mail | 16 | None | 13 | Yes |
| Splint | 17 + Dex (max 2) | +2 | 15 | Yes |
| Plate | 18 | None | 15 | Yes |
| Shield | +2 to AC | None | None | No |
3. Dexterity Modifier and AC
The Dexterity modifier plays a crucial role in AC calculations for most armor types. The basic rules are:
- Light armor (Padded, Leather, Studded Leather) adds your full Dexterity modifier
- Medium armor (Hide, Chain Shirt, Scale Mail, Breastplate, Half Plate) adds your Dexterity modifier up to a maximum of +2
- Heavy armor (Ring Mail, Chain Mail, Splint, Plate) doesn’t add your Dexterity modifier at all
- Shields add a flat +2 bonus regardless of armor type
For characters with the Mage Armor spell (or similar effects), the calculation becomes:
AC = 13 + Dexterity Modifier
4. Special AC Modifiers
Several game mechanics can temporarily modify your AC:
- Defensive Fighting Style: +1 to AC (Fighter class feature)
- Dodge Action: Imposes disadvantage on attacks against you until your next turn
- Cover:
- Half Cover: +2 to AC and Dexterity saving throws
- Three-Quarters Cover: +5 to AC and Dexterity saving throws
- Total Cover: Can’t be targeted directly
- Magic Items: Many magical items provide AC bonuses, typically +1, +2, or +3
- Class Features: Some classes have features that modify AC, like the Monk’s Unarmored Defense or the Barbarian’s Unarmored Defense
5. Unarmored Defense Options
Several classes provide alternative AC calculations when not wearing armor:
| Class | AC Calculation | Requirements |
|---|---|---|
| Barbarian | 10 + Dex + Con | Not wearing armor, not using shield |
| Monk | 10 + Dex + Wis | Not wearing armor, not using shield |
| Dragon Sorcerer | 13 + Dex | Not wearing armor |
| Warlock (Hexblade) | 10 + Dex + Cha (max Cha) | Not wearing armor, not using shield |
6. Common AC Misconceptions
Many players new to D&D 5e make these common mistakes about AC:
- Stacking Shields: You can only benefit from one shield at a time, even if you’re somehow wielding two
- Dexterity Caps: Forgetting that medium armor caps Dexterity bonuses at +2
- Magic Armor Stacking: Magic bonuses from different items don’t stack unless they specify they do
- Unarmored Defense: Thinking you can add a shield bonus to unarmored defense (you can!)
- Dodge and AC: The Dodge action doesn’t increase your AC, it imposes disadvantage on attacks against you
7. Optimizing Your AC
To maximize your Armor Class, consider these strategies:
- Choose the Right Armor: For most characters, the best non-magical armor is:
- High Dexterity: Studded Leather + Shield (AC 12 + Dex + 2)
- Medium Dexterity: Half Plate + Shield (AC 17 + 2)
- Low Dexterity: Plate + Shield (AC 20)
- Magic Items: Prioritize:
- +1, +2, or +3 armor
- +1, +2, or +3 shields
- Cloaks or rings that provide AC bonuses
- Class Features: Consider classes with strong AC features:
- Fighter (Defensive fighting style)
- Barbarian (Unarmored Defense with Constitution)
- Monk (Unarmored Defense with Wisdom)
- Spells: Several spells can boost AC:
- Mage Armor (AC 13 + Dex)
- Shield (AC +5 until next turn)
- Barkskin (AC becomes 16, if lower)
- Positioning: Use cover effectively in combat to gain additional AC bonuses
8. AC by Character Level (Average Values)
Here’s what you can typically expect for AC at different character levels:
| Level Range | Low AC (Unoptimized) | Average AC | High AC (Optimized) |
|---|---|---|---|
| 1-4 | 12-14 | 15-17 | 18-20 |
| 5-10 | 14-15 | 17-19 | 20-22 |
| 11-16 | 15-16 | 19-21 | 23-25 |
| 17-20 | 16-17 | 21-23 | 25+ |
9. How AC Affects Game Balance
AC plays a crucial role in the game’s balance mechanics:
- Bounded Accuracy: D&D 5e uses a system where attack bonuses increase slowly as characters level up. This means that even at high levels, a very high AC remains valuable
- Monster CR: Challenge Rating takes into account both offensive and defensive capabilities. A monster with high AC but low damage output might have a lower CR than one with balanced stats
- Action Economy: Spells and abilities that temporarily boost AC (like Shield) are powerful because they don’t require using your action
- Save vs. Attack: Many effects give you a choice between making a saving throw or being hit by an attack roll. High AC can make attacks more appealing for enemies to use against you
10. Historical Context of Armor in D&D
The concept of Armor Class has evolved significantly through D&D’s editions:
- Original D&D (1974): AC started at 9 (best) and went down to 2 (worst), with lower numbers being better
- AD&D (1977): Introduced the concept of ascending AC (10 as base) but kept the “lower is better” for attack rolls
- D&D 3rd Edition (2000): Standardized ascending AC where higher numbers are better, which continues in 5e
- D&D 4th Edition (2008): AC became one of several defenses (along with Fortitude, Reflex, and Will)
- D&D 5th Edition (2014): Returned to the simpler AC system while maintaining bounded accuracy
For more historical context on armor in medieval warfare (which inspired D&D’s armor system), you can explore these authoritative resources:
- The Metropolitan Museum of Art’s Arms and Armor Collection
- Royal Armouries Museum (UK)
- Library of Congress Digital Collections on Historical Armor
11. Advanced AC Calculations
For characters with multiple AC-modifying effects, the calculations can become complex. Here’s how to handle special cases:
- Multiple AC Sources: When you have multiple effects that set your AC (like Unarmored Defense and Mage Armor), you choose which one to use
- Temporary Bonuses: Effects like the Shield spell add to your current AC, regardless of how it was calculated
- Situational Modifiers: Cover bonuses and the Dodge action’s disadvantage apply after all other calculations
- Magic Item Stacking: Unless an item specifies otherwise, you can’t benefit from multiple items of the same type (e.g., two +1 shields)
- Size Modifiers: Very large or very small creatures might have AC adjustments, though this is rare in 5e
Example complex calculation:
A level 5 Monk (Wisdom 16, Dexterity 18) with a +1 Shield and the Defensive fighting style:
- Base AC: 10 + Dex (4) + Wis (3) = 17
- Shield: +1 (magic) +1 (base) = +2
- Defensive Style: +1
- Total AC: 17 + 2 + 1 = 20
12. AC and Character Builds
Different character concepts will prioritize AC differently:
- Tanks (Paladins, Fighters): Aim for AC 20+ with heavy armor and shields
- Skirmishers (Rogues, Rangers): Focus on medium armor with high Dexterity (AC 17-19)
- Spellcasters (Wizards, Sorcerers): Often rely on Mage Armor (AC 13-17) or high Dexterity
- Hybrids (Clerics, Druids): Balance between armor and other attributes (AC 16-18)
Remember that AC isn’t the only defensive statistic – hit points, saving throws, and resistances all contribute to your character’s survivability.
13. Common House Rules for AC
Many DMs implement house rules to modify AC calculations. Some popular ones include:
- Dexterity Cap Removal: Allowing full Dexterity bonuses with medium armor
- Armor as DR: Converting some AC bonuses into damage reduction instead
- Shield Mastery: Allowing shields to provide additional benefits beyond +2 AC
- Armor Training: Letting characters reduce or eliminate strength requirements or stealth disadvantages
- AC Penalties: Applying penalties for encumbrance or damaged armor
Always discuss any house rules with your DM before creating your character to ensure your AC calculations will be correct for their game.
14. Mathematical Analysis of AC
Understanding the probability behind AC can help you make better decisions:
- Each +1 to AC reduces an enemy’s chance to hit by about 5% (assuming a typical attack bonus)
- At level 1, an AC of 16 means most monsters will hit on a 13+ (40-45% chance)
- By level 5, that same AC 16 might be hit on a 10+ (55% chance) as attack bonuses improve
- AC 20 at level 10 typically means enemies need a 15+ to hit (about 30% chance)
- The “sweet spot” for AC is usually 2-3 points higher than the average attack bonus you face
You can use this calculator to experiment with different AC values and see how they interact with typical attack bonuses at various levels.
15. Final Tips for Maximizing AC
- Always carry a shield if you can – the +2 bonus is one of the most cost-effective AC boosts
- For spellcasters, Mage Armor is often better than light armor unless you have very high Dexterity
- Don’t neglect Dexterity – even heavy armor characters benefit from better initiative and saving throws
- Consider magical items that provide AC bonuses as top priorities
- Use cover effectively in combat – those +2 or +5 bonuses can be the difference between life and death
- Remember that some AC bonuses (like from the Dodge action) don’t stack with themselves
- If playing a Monk or Barbarian, invest in both Dexterity and Wisdom/Constitution for maximum unarmored AC
- At higher levels, look for ways to combine multiple AC bonuses (magic armor + shield + fighting style)