Everything in Dungeons & Dragons has an AC or Armor Class. This number indicates how difficult that thing is to harm. Determining AC for players is relatively easy, however, how do you know the AC of, say, a door? And how do you describe a missed attack in a way that isn’t repetitive or boring? That’s where this quick guide comes in!
How do you determine AC in Dungeons & Dragons 5e?
- To determine is an attack “hits,” roll a d20 and add any modifiers if the number is equal to or greater than the creature’s armor class, the attack hits.
- To determine your players or NPCs base Armor Class, you simply add 10 + their Dexterity modifier.
- To determine the AC of objects, decide how difficult they are to break. A wooden door might have an Armor Class of 11, but a metal chest will have an AC of 14.
Your Player’s Armor Class
The base AC of your players determines how difficult they are to hit. When rolling an attack, if the number rolled plus any modifiers is equal to or greater than the armor class, the attack hits.
For flavor in your descriptions, you can attribute a missed attack to either the player’s dexterity or armor, but either way, the number that determines AC comes from the player’s Dexterity modifier.
The higher the player’s AC, the more difficult it is for enemies to land a hit on them. Most players will not start with a high AC, but there are several ways for Players or NPCs to raise their AC.
Armor and Shields
Armor and shields both serve to increase AC, but players must have proficiency with the armor they are wearing or the will suffer penalties to ability checks.
Most players think they can jump into whatever set of armor they want and start fighting like normal, but it takes a lot of training to be able to fight in armor. Class determines proficiency, and if players do not have proficiency in the armor they are wearing, then the following penalties apply:
- Disadvantage on Strength & Dexterity Ability Checks
- Disadvantage on Strength & Dex Saving Throws
- Disadvantage on Attacks that relies on Strength or Dexterity
- Cannot cast Spells
Unlike armor, anyone can use a shield. A shield adds +2 to Armor Class and does not pose any disadvantages other than it requires one hand to wield. This means that if a weapon requires two hands to use, then the player cannot wield the shield and use that weapon at the same time.
Likewise, if a spell requires two hands to cast, the player must first put away or drop the shield before casting, lower their armor class by 2.
Armor Class by Armor Type
| Armor | Armor Class (AC) | Strength Required | Disadvantage to Stealth |
| Light Armor | |||
| Padded | 11 + Dex Mod | – | Yes |
| Leather | 11+ Dex Mod | – | |
| Studded | 12 + Dex Mod | – | |
| Medium Armor | |||
| Hide | 12 + Dex Mod | – | |
| Chain Shirt | 13 + Dex Mod | – | |
| Scale mail | 14 + Dex Mod | – | Yes |
| Breastplate | 14 + Dex Mod | – | |
| Half Plate | 15 + Dex Mod | – | |
| Heavy Armor | |||
| Ring Mail | 14 | – | Yes |
| Chain mail | 16 | 13 | Yes |
| Splint | 17 | 15 | Yes |
| Plate | 18 | 15 | Yes |
Selling Armor & Weapons
As your party levels up and gains gold, they will likely want to upgrade their weapons and armor. This means they will be looking to sell their old gear or maybe even sell the armor and weapons they come across on their adventures.
A good rule of thumb is that undamaged armor and weapons used by players will sell for half or less of their cost (see chart below).
| Armor (Non-Magical) | Cost | Undamaged Selling Price | Damaged Selling Price |
| Light Armor | |||
| Padded | 5 gp | 2 gp | 2 silver |
| Leather | 10 gp | 5 gp | 1 gp |
| Studded Leather | 45 gp | 22 gp | 10 gp |
| Medium Armor | |||
| Hide | 10 gp | 5 gp | 1 gp |
| Chain Shirt | 50 gp | 25 gp | 12 gp |
| Scale mail | 50 gp | 25 gp | 12 gp |
| Breastplate | 400 gp | 200 gp | 50 gp |
| Half plate | 750 gp | 375 gp | 100 gp |
| Heavy Armor | |||
| Ring mail | 30 gp | 15 gp | 3 gp |
| Chain mail | 75 gp | 37 gp | 10 gp |
| Splint | 200 gp | 100 gp | 40 gp |
| Plate | 1,500 gp | 750 gp | 300 gp |
| Shield | |||
| Shield | 10 gp | 5 gp | 2 silver |
Pulling Armor Off Dead Enemies
Perhaps your party likes to save money by trying to salvage armor from dead enemies. While this might seem economical, in real life it is unlikely that such items would actually fit.
Unlike weapons that are universal in size, armor is fitted to the individual. This means one person’s armor is not likely to fit another person perfectly. While the armor will still offer the same level of protection, ill-fitting armor is likely to impose disadvantages.
If a player chooses to use armor that does not fit them, they have the same disadvantages as if they were not proficient in the armor type until they get it altered. This ruling allows players to save money (alternations are far cheaper than buying the set of the armor itself) but maintains a logical sense of reality.
The Armor Class of Objects
Most often your players will be trying to hit enemies. Each monster stat box will include the monster’s AC. However, there are times when your players will be aiming for inanimate objects which do not have a dexterity modifier. How do you determine the AC of objects?
While AC can refer to how quickly something can dodge out of the way of attacks, it can also relate to how hefty something is. Objects that are easily broken will have a low AC, while sturdy objects will have a much higher AC. See the chart below for a helpful reference.
| Objects | Armor Class |
| Vase, glass pane, porcelain figure, plates, pottery | 1-5 |
| Most small/medium wooden objects | 6-10 |
| Solid wooden doors, wooden chests | 11-15 |
| Metal doors, metal chests, locks (if trying to break), stone objects | 16-18 |
| Arcane objects, extremely sturdy objects | 19-20 |
| diamond, mithril | 20-25 |
| Items that are nearly impossible to break | 26-30 |
Describing Missed Attacks
When your players or monsters miss an attack, instead of just saying “They miss you,” and moving on, try using some of these phrases:
- The attack glances off your armor leaving a long scratch on the metal
- At the last moment, you raise your shield, forcing the attack to bounce off harmlessly
- You fire your arrow, it hits just where you aimed, but you watch as it shatters against the iron scales of the beast
- You raise your sword and bring it down in an arc strike, but the enemy jumps nimby over your attack, avoiding it
- The monster lunges at you, you hold up your sword, catching it before its jaws sink into your neck. It snaps at you madly, unable to reach you before you throw it off
Remember, even missed attacks can be opportunities for epic battle descriptions! Make them just as interesting as your successful attacks if you want to keep your players engaged.
Everything has an Armor class. AC is one of the most useful machines in the game and you can use it in a variety of ways to add depth and flavor to your campaign.
Now that you know the ins and out of Armor Class, you should always know what hits and what doesn’t.
Until next time,
May your game have advantage, my friends!
-Halfling Hannah
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