How Armor Class Works in D&D 5e
Without armor your AC is 10 plus your Dexterity modifier; armor, Unarmored Defense or Mage Armor gives you a different base, and a Shield adds 2. Armor Class is the number every attack roll aims at. SRD 5.2.1 puts it in one line:
An Armor Class (AC) is the target number for an attack roll. AC represents how difficult it is to hit a target.
Hit it or beat it and the attack lands. Here is how you get yours, and what each point is worth.
The starting number
With nothing on, everyone has the same formula:
Your base AC calculation is 10 plus your Dexterity modifier. If a rule gives you another base AC calculation, you choose which calculation to use; you can't use more than one.
That last sentence matters. Armor, Unarmored Defense and Mage Armor are all base AC calculations. You pick one. They never stack.
The armor table
| Armor | AC | Strength | Stealth | Cost |
|---|---|---|---|---|
| Padded | 11 + Dex | Disadvantage | 5 GP | |
| Leather | 11 + Dex | 10 GP | ||
| Studded Leather | 12 + Dex | 45 GP | ||
| Hide | 12 + Dex (max 2) | 10 GP | ||
| Chain Shirt | 13 + Dex (max 2) | 50 GP | ||
| Scale Mail | 14 + Dex (max 2) | Disadvantage | 50 GP | |
| Breastplate | 14 + Dex (max 2) | 400 GP | ||
| Half Plate | 15 + Dex (max 2) | Disadvantage | 750 GP | |
| Ring Mail | 14 | Disadvantage | 30 GP | |
| Chain Mail | 16 | Str 13 | Disadvantage | 75 GP |
| Splint | 17 | Str 15 | Disadvantage | 200 GP |
| Plate | 18 | Str 15 | Disadvantage | 1,500 GP |
| Shield | +2 | 10 GP |
Light armor adds all your Dexterity. Medium adds up to 2. Heavy adds none. Light armor takes 1 minute to put on or take off; Medium 5 minutes on and 1 off; Heavy 10 on and 5 off. Sleeping in Plate is not an option when the camp gets ambushed.
The Strength column is a speed rule, not a ban:
If the table shows a Strength score in the Strength column for an armor type, that armor reduces the wearer's speed by 10 feet unless the wearer has a Strength score equal to or higher than the listed score.
Training, or the armor works against you
Anyone can don armor or hold a Shield, but only those with training can use them effectively.
Wear armor without training and the cost is steep:
If you wear Light, Medium, or Heavy armor and lack training with it, you have Disadvantage on any D20 Test that involves Strength or Dexterity, and you can't cast spells.
A Shield without training gives nothing at all. And one of each, at most:
A creature can wear only one suit of armor at a time and wield only one Shield at a time.
Fighters and Paladins train in all armor and Shields. Clerics, Rangers and Barbarians get Light and Medium and Shields; Druids Light armor and Shields; Bards, Rogues and Warlocks Light armor only. Monks, Sorcerers and Wizards get none.
Three ways to fight without armor
Barbarian, Unarmored Defense:
While you aren't wearing any armor, your base Armor Class equals 10 plus your Dexterity and Constitution modifiers. You can use a Shield and still gain this benefit.
Monk, Unarmored Defense:
While you aren't wearing armor or wielding a Shield, your base Armor Class equals 10 plus your Dexterity and Wisdom modifiers.
The Barbarian keeps the Shield. The Monk cannot.
Mage Armor, a level 1 Sorcerer and Wizard spell lasting 8 hours:
You touch a willing creature who isn't wearing armor. Until the spell ends, the target's base AC becomes 13 plus its Dexterity modifier. The spell ends early if the target dons armor.
Six level 1 heroes
| Hero | Gear | AC |
|---|---|---|
| Wizard, Dex 14 | Nothing | 12 |
| Wizard, Dex 14 | Mage Armor | 15 |
| Rogue, Dex 16 | Leather | 14 |
| Monk, Dex 16, Wis 14 | Unarmored Defense | 15 |
| Barbarian, Dex 14, Con 16 | Unarmored Defense, Shield | 17 |
| Cleric, Dex 14 | Chain Shirt, Shield (starting gear) | 17 |
| Fighter, Str 16 | Chain Mail (starting gear), Shield | 18 |
Mage Armor is worth 3 AC to a Wizard for one spell slot a day. The Rogue gains 1 by saving up 35 GP more for Studded Leather. A Cleric with Dex 14 loses nothing to the Medium cap; at Dex 16 or more, Light armor starts to catch up.
What one point buys
A Goblin Warrior's Scimitar hits with +4. An Ogre's Greatclub hits with +6 and deals 13 (2d8 + 4). Each point of AC takes 5 percentage points off every attack, natural 1s and 20s aside:
| AC | Goblin hits | Ogre hits | Ogre damage per swing |
|---|---|---|---|
| 12 | 65% | 75% | 10.2 |
| 14 | 55% | 65% | 8.9 |
| 15 | 50% | 60% | 8.25 |
| 16 | 45% | 55% | 7.6 |
| 17 | 40% | 50% | 6.95 |
| 18 | 35% | 45% | 6.3 |
| 20 | 25% | 35% | 5.0 |
The 5 points stay the same, but the share they cut grows. AC 12 to 14 cuts the Goblin's hits by 15%. AC 16 to 18 cuts them by 22%. Every point is worth more than the one before it.
The Wizard who casts Mage Armor turns an Ogre's 75% into 60%: one swing in five that would have landed now misses. The Fighter who saves 1,425 GP to swap Chain Mail for Plate takes the Ogre from 55% to 45%, nearly a fifth fewer hits, for the rest of the campaign.
Quick rules for the table
- Pick one base calculation. Armor, Unarmored Defense or Mage Armor. A Shield adds +2 on top of any of them except the Monk's.
- Check the Strength column before buying Chain Mail, Splint or Plate.
- Check the Stealth column if your hero sneaks. Breastplate gives 14 + Dex without the Disadvantage.
- Never wear armor without training. You lose spellcasting and take Disadvantage on Strength and Dexterity rolls.
- Count your AC up from the formula, then check the sheet. Our sheet walkthrough does it box by box.
This work includes material from the System Reference Document 5.2.1 ("SRD 5.2.1") by Wizards of the Coast LLC, available at dndbeyond.com/srd. The SRD 5.2.1 is licensed under the Creative Commons Attribution 4.0 International License.
