Armor Class (AC) in D&D 5e represents how hard it is to hit a creature or character, and figuring it out is straightforward once you understand the core rules. This guide walks through the default formula, typical modifiers, and how different classes and abilities influence AC, so you can quickly determine your defensive number at the table. Whether you are new to the game or want a reliable reference, the steps below will help you resolve AC checks accurately and consistently.
Core Armor Class Formula in 5e
Dungeons & Dragons 5th Edition uses a simple rule to determine AC: 10 plus your Dexterity modifier plus any other modifiers that apply. This baseline covers creatures that wear light or no armor and rely on agility. If you are wearing armor or using a shield, you add the armor or shield’s base value instead of relying solely on Dexterity. The goal is to keep AC easy to calculate at a glance, so you know your target number for attackers to meet or beat to hit you.
How to Determine Your Base Armor Type
Light Armor, Medium Armor, and Heavy Armor
Light armor such as leather or padded typically provides an AC of 10 or 11 and usually allows full Dexterity bonus usage. Medium armor like chainmail grants higher AC but may limit how much of your Dexterity modifier you can add. Heavy armor, including plate, sets a higher AC baseline but often caps or removes the Dexterity bonus entirely. Your character sheet or the Player’s Handbook lists each armor’s AC value, proficiency requirement, and any movement or speed penalties. Choosing the right balance between protection and mobility shapes how you compute your final AC.
Shields as an AC Booster
A shield is one of the most reliable ways to raise AC, adding a flat bonus of 2 to your total regardless of armor type. Unless a rule or effect states otherwise, you add this shield bonus on top of your armor’s base AC and any applicable Dexterity modifier. Because shields consume a hand, they trade one attack or an action for improved defense, so weigh the benefit against your tactical needs.
Dexterity Modifier and Its Impact on AC
Dexterity represents agility, reflexes, and balance, and its modifier is central to AC for most characters. A positive Dexterity modifier increases AC, making you harder to hit, while a negative modifier lowers it. Barbarians using Unarmored Defense and certain class features can replace Dexterity with Constitution or another ability score for AC, but most players rely on Dexterity when not wearing restrictive armor. Always double-check whether your class, features, or spells change how Dexterity applies to AC.
Calculating AC With Common Scenarios
To figure out AC in practice, start with your base armor value, add your Dexterity modifier unless restricted, then add any shield bonus. For example, a character in chainmail (AC 16) with a Dexterity modifier of +3 and a shield would have AC 18: 16 plus 2 from the shield. A character in leather (AC 11) with a Dexterity modifier of +2 and no shield has AC 13, derived from 10 plus Dexterity. Use a character sheet or quick reference table to streamline repeated calculations during a session.
Special Rules and Exceptions to Remember
Unarmored Defense and Class Features
Some classes, like Monks and Barbarians, use Unarmored Defense, which replaces traditional armor calculations. A Monk’s AC equals 10 plus Dexterity modifier plus their Wisdom modifier, provided they are not wearing armor or using shields. Barbarians use Constitution instead of Dexterity for Unarmored Defense, yielding a formula of 10 plus Constitution modifier plus Dexterity modifier when not encumbered. Other class features, such as the Defender Spirit option for Barbarians, further tweak these rules, so confirm which modifiers apply in each circumstance.
Spells, Magical Items, and Special Conditions
Spells like Mage Armor set AC as 13 plus Dexterity modifier, and items such as cloaks of protection add a fixed bonus to AC that stack with armor and shield values where allowed. Conversely, conditions like being restrained or blinded do not directly change AC, but they may affect your ability to benefit from Dexterity or other modifiers. Always read the specific wording on magical effects, because they can override standard rules or interact in unexpected ways.
Practical Tips for Players and DMs
- Memorize the core formula: 10 + Dexterity modifier + armor value + shield bonus (if applicable).
- Verify whether your armor or class feature caps or modifies your Dexterity bonus.
- Update AC on your sheet whenever you change armor, gain a shield, or acquire a bonus.
- Use a character sheet tool or quick reference card to avoid slowing down combat.
- Ask your DM about unusual interactions, such as homebrew rules or specific magic items that affect AC.
Summary Table: Example AC Calculations
| Armor Type | Dexterity Modifier | Shield Used | Resulting AC |
|---|---|---|---|
| Leather (AC 11) | +2 | No | 13 (10 + 2) |
| Chainmail (AC 16) | +3 | Yes | 18 (16 + 2 + 1 from shield) |
| Plate (AC 18) | +1 | No | 18 (capped by armor) |
| No armor, Unarmored Defense | +2 | No | 13 (10 + 2) |
Figuring out armor class in D&D 5e becomes routine when you follow the base rules and account for armor, Dexterity, and shields step by step. By understanding exceptions and class-specific options, you avoid surprises at the table and make faster, more confident decisions. Keep this process in mind each session, and you will quickly calculate accurate AC values for any character or creature.