When it comes to combat in any game, you typically want to hit with many attacks without getting hit yourself. Whether you want to dance over swords while singing “Can’t Touch This,” have arrows bounce off your rippling muscles, or stop a blade with your gleaming plate mail, in dungeons and dragons, we have something called Armor Class -often shortened to AC – which helps you do this very thing.
Now figuring out how to calculate AC is an excellent skill to have and is very easy! For any unarmored character/creature, start with 10, and add the Dexterity Modifier alongside any other bonuses. Simple! Armor is a little more tricky:
Light armor and the mage armor spell, they change the 10 in that formula
Medium armor however only adds up to +2 to your AC from Dexterity (+3 if you have the Medium Armor Master feat)
Heavy armor ignores Dexterity altogether, be careful of Strength Requirements. If you don’t meet the Strength requirement listed for your chosen Heavy Armor, then your movement speed will be reduced by 10ft unless you’re a Dwarf.
Of course, there are features such as the Barbarian’s and Monk’s Unarmored Defense abilities that can also increase AC. However, such features typically tell you how to calculate AC. Some cases give you a flat AC number to use, such as the Tortle’s natural AC or the Barkskin spell. Other than that, you only need to keep track of magic items, magical effects, shields, and additional bonuses to AC.
Tip: AC calculations don’t stack! If you have two different ways of determining your AC, for example, a Tortle Barbarian, you would need to choose between the Tortle’s fixed 17 AC or the Barbarians Unarmored Defense formula. Bonuses to AC like shields and magic items will still apply unless the AC giving feature says otherwise.
Now that you know, I see a high AC build in your future. Good Luck, and don’t die!