Scaling AC (5e Variant Rule)
From D&D Wiki
While many other things (such as damage and hit points) scale with a character's level in 5e, AC doesn't. There are plenty of systems that have scaling defenses, and this adds AC that scales to your level to 5e.
A creature's base (or unarmored) AC equals 8 + its proficiency bonus + its Dexterity modifier. This never changes unless otherwise specified.
A character proficient a set of armor adds its proficiency bonus to the AC granted by the armor. A creature that does not do such simply gains the AC of the armor. When a character not proficient with a a set of armor attempts to cast a spell while wearing such armor, it must make an ability check using its spellcasting ability. For light armor, the DC is 10. For medium armor, the DC is 12. For heavy armor, the DC is 15. On a failure, the spell fizzles, and any resources expended to cast it are wasted.
The tables below denote the AC provided by each set of armor:
|Padded||9 + Dex|
|Leather||10 + Dex|
|Studded Leather||11 + Dex|
|Hide||10 + Dex (max 2)||No|
|Chain Shirt||11 + Dex (max 2)||No|
|Scale Mail||12 + Dex (max 2)||Yes|
|Breastplate||12 + Dex (max 2)||No|
|Half Plate||13 + Dex (max 2)||Yes|
|Heavy Armor||AC||Strength Requirement||Disadvantage?|
Class Feature Changes
- Unarmored Defense (Barbarian)
While you are not wearing any armor, your Armor Class equals 8 + your proficiency bonus + your Dexterity modifier + your Constitution modifier. You can use a shield and still gain this benefit.
- Unarmored Defense (Monk)
Beginning at 1st level, while you are wearing no armor and not wielding a shield, your AC equals 8 + your proficiency bonus + your Dexterity modifier + your Wisdom modifier.
The target's AC can't be lower than 14 + your proficiency bonus.
- Divine Armor
The target's AC becomes 8 + your proficiency bonus + its Dexterity modifier + half your spellcasting modifier.
- Mage Armor
The target's AC becomes 11 + your proficiency bonus + its Dexterity modifier.
- Mirror Image
The images' AC equals 8 + your proficiency bonus + your Dexterity modifier.