Armour

Damage Reduction reduces physical damage taken. Elemental damage and damage-over-time are not affected. The amount of damage reduction depends on the defender's armour total, and the attacker's attack damage:

reduction = armour / (armour + 12*damage)

The amount of reduction is capped, it cannot be more than 95%.

The fact that damage reduction scales with the amount of damage means it is difficult to know exactly how much damage is being reduced. An easy to remember rule of thumb is that to achieve 50% damage reduction, you will need an armour rating equal to twelve times that of the damage being dealt. For example, to achieve 50% damage reduction against a 100 damage hit, you'll need 1200 armour.