Leather Armor provides one point of armor if it covers the torso, it provides another point if it protects at least four of your five limbs (head, arms, and legs). If more than than 50% of the leather on the torso is studded then you receive an additional point of armor.
Chain Armor provides two points of armor if it covers the torso, it provides another point if it protects at least three of your five limbs (head, arms, and legs).
Plate Armor provides three points of armor if it covers the torso, it provides another point if it protects at least two of your five limbs, and two points if it covers four of your five limbs.
Any combonation of armor which totals 4 or 5 points of armor is considered to be "Heavy" armor and suffers the trait requirements of heavy armor.There is a myriad of different types of armor throughout history and in fantasy. Below is a sampling of these types and which class they fall into our groupings. Leather: Padded Cloth, Chain Mail Bikini
Leather w/ studs: Hide, Wicker/Bamboo, Ring Mail
Chain: Brigandine, Scale Mail, Plate Mail Bikini
Plate: Lamellar, Banded, Splinted
Coverage: for armor to give its full benefit, it must cover more than half of the torso or limb that it is to be protecting. If the armor covers less than half the area that it is protecting and more than one third then it is treated as if it was armor of a class one level lower than it. For example a Plate bracer that reaches from the wrist to the elbow would count as fully protecting that arm as plate armor. If it only reached from the wrist to just over halfway up the forearm, then it would count as chain. Steel bracelets that cover only the wrists would not count as armor at all.
Helmets: a helmet must fit on the head and not fall off when the player bends over ninety degrees at the waist, this is primarily for safety.
Piecemeal Armor: Most Armor is actually a combination of two or more types of armor layered for extra protection and comfort. When determining the protection of piecemeal armor you count the piece that gives the highest value only. So if you are wearing full leather sleeves and plate bracers that reach from the wrist to the elbow, you would count it as plate armor because they provide the greatest protection even though the leather is providing the greater coverage.
Item Tags: Armor is given in game tags as suits of armor and not as seperate pieces. This means that if a suit of armor's total value is between 1 and 3 it counts as light armor for the purposes of crafting and trait requirements. If a suit's full armor value equals 4 or 5 then it counts as heavy armor for the purpose of crafting and trait requirements.