The armor class system that AD&D as presented has never been clearly defined or explained, especially in such strange situations where a character would have better AC when surprised then when in combat. Also, it has always been a mystery why they counted down into negative numbers instead of up. The 3rd edition of game rightly decided to count upwards but failed to take it to the next step to fully explain where each point of AC comes from.

We will divide defense class into three different categories: base AC for size, armor provided AC, and dexterity provided AC. This system will allow for easy calculations when attacks ignore dexterity or when they ignore armor. However, the high dexterity characters will notice that their reflexes will be slowed by wearing heavier armors, but this makes a lot of sense and will force some decision making when creating a character. Still, their will be a skill added to the fighter class called Armor Use, this skill will provide a way for a warrior to train in a particular form of armor and eleviate some of the dexterity limiting effects.

Base Armour Class by Size Fine = 13 Diminutuve = 9 Tiny = 7 Small = 6 Medium = 5 Large = 4 Huge = 3 Gargantuan = 1 Colossal = 0 Dexterity Adjustment for Armor (rounded up) Light or No Armor = DEX/2 Medium Armor = DEX/3 Heavy Armor = DEX/5 Armor’s Base Defense, Weight Classes, and Cost Padded AC = 1 Light 5gp Leather AC = 2 Light 10gp Studded or Ring AC = 3 Light 25gp or 35gp Hide AC = 5 Medium 15gp Scale or Brigantine AC = 6 Medium 50gp or 75gp Chain AC = 7 Medium 150gp Breastplate AC = 8 Medium 250gp Splint AC = 9 Heavy 200gp Banded; AC = 10 Heavy 250gp Half Plate AC = 11 Heavy 600gp Full Plate AC = 12 Heavy 1500gp