To increase AC, you can wear items of Armour (1 per body area)  Each item of Armour has an AP rating. All worn items of Armour produce a Total AP number.

Armour Point Bonus (APB) is your Total AP minus half (rounded up).

Your AC stat is calculated using the formula 12 + APB + Dexterity Modifier.

If your AP exceeds the total of your Strength x 2, Or the total of your Strength Modifer + Dexterity Modifier – you will become Encumbered.

If your AP exceeds BOTH the total of your Strength x 2 and the total of your Strength Modifier + Dexterity Modifier – you will become Heavily Encumbered.

(It takes 1 Actions per Armour point to Donn or Doth the item of Armour)

Legs:

Light 1 AP: Padded / Leather /  Studded leather 5-50 gp | 1-2kg
Medium 2 AP: Splint / Plate / Scale 50-500 gp  | 2kg to 3kg 

Arms / Hands:

Light 1 AP: Padded / Leather /  Studded leather 5-50 gp | 1-2kg
Medium 2 AP: Splint / Plate / Scale 50-500 gp  | 2kg to 3kg 

Torso:

Light 1 AP: Padded / Leather 15 gp | 2kg
Medium 2 AP: Splint / Studded leather / Chain 150 gp | 3kg
Heavy 3 AP: Plate 1500 gp | 4kg

Head:

Light 2 AP: Leather (hood/cap) 10 gp | 1kg
Medium 3 AP: Chainmail Hood 100 gp | 2kg
Heavy 4 AP: Plate skullcap/helm/bassinet 1000 gp | 3kg

Shield:

Small 2 AP: Small Wooded 20 gp | 2-3kg
Large 3 AP:  Large Wood, Small Metal 40 gp | 4-5kg