Defense

Defense is a player statistic that determines how much damage can be taken per hit. On non-Expert mode worlds, the damage the player takes is reduced by half of their defense value, altogether. In Expert mode, damage the player takes is reduced by three-quarters of their defense value, rounded up. Defense can be increased by equipping armor and accessories, or temporarily boosted by various buffs. No attack can be reduced below 1 damage (with the exception of a player with an ally wearing the Paladin's Shield).

Some forms of damage are impossible to reduce through defense. Damage from health-draining Debuffs like Cursed Inferno, drowning in water, or colliding with a boulder are not reduced by defense.

Damage taken from lava can be reduced through defense.

Mechanics

Defense gives a flat reduction in damage: i.e. damage is reduced by a fixed amount per hit (as opposed to a multiplicative damage reduction, which would reduce damage by a percentage).

Normal mode Formula

The formula is:

net damage = attack - (defense * 0.5)

For example:

• With 20 Defense, a 40 Damage attack is reduced by 10, resulting in 30 damage taken.
• With 30 Defense, a 40 Damage attack is reduced by 15, resulting in 25 damage taken.

Expert mode Formula  

In expert mode, the formula is:

net damage = attack - (defense * 0.75)

For example:

• With 20 Defense, a 40 Damage attack is reduced by 15, resulting in 25 damage taken.
• With 30 Defense, a 40 Damage attack is reduced by 23, resulting in 17 damage taken.

Note that in expert mode only the player's defense follows the formula. Enemies will still take the same amount of damage as in normal mode.

Enemies

Enemies have a defense statistic just like players do, but they do not gain more protection from defense in Expert mode. Enemies will always reduce incoming damage by 50% of their defense regardless of difficulty. Monsters with high defense will take virtually no damage from low damage weapons (e.g. Fire Imps take 5 damage from the Minishark with Musket Balls). Accordingly, when fighting high defense monsters, high damage weapons are preferable.

Armor

Armor is a set of equipable defense items that reduce damage taken from enemies and most other damage sources. Armor pieces are equipped by placing them in the Armor slots of the player's inventory. Armor can also be placed in vanity slots to change the player's appearance without affecting stats.

In addition to the defense provided by individual Armor pieces, most Armor types provide a "Set Bonus" when all three pieces of the same Armor type are worn simultaneously. For the basic pre-Hardmode Ore armors (Copper, Tin, Iron, Lead, Silver, Tungsten, Gold, and Platinum), this is an additional defense bonus. More advanced or unique Armors can provide other specialized set bonuses (e.g. the Shroomite Armor will provide invisibility when not moving).

See the full page here, which includes an overview, a full list of armor types, and descriptions of each armor set.

Defense boosts

Here is a list of accessories, and their respective defense bonuses. A list of armor including defenses can be found on the armor page.

Item	Accessory Defense
Shackle	1
Cobalt Shield	1
Obsidian Skull	1
Shield of Cthulhu	2
Obsidian Shield	2
Moon Charm	3 (only during the night)
Moon Shell	3 (only during the night)
Moon Stone	4 (only during the night)
Sun Stone	4 (only during the day)
Celestial Stone	4
Ankh Shield	4
Paladin's Shield	6 (Absorbs 25% of damage done to players on your team, Only active above 25% life)
Celestial Shell	4 (during the day) 7 (during the night)
Flesh Knuckles	7
Frozen Turtle Shell	0 until below 50% health when it reduces total damage by 25%   30 (When below 25% health)
Modifiers	4 (Max per accessory)
Buff / Debuff	Temporary Defense
Well Fed	2
Dryad's Blessing	8
Ironskin	8
Tipsy	Defense reduced by 4
Weak	Defense reduced by 4
Ichor	Defense reduced by 20
Broken Armor	Defense reduced by half

Damage reduction boosts

All damage reduction boosts (except Paladin's Shield) affect damage taken after defense.

Buff	Source	Damage reduction bonus
Solar Blaze	Solar Flare armor	30%
Beetle Endurance	Beetle armor	15% / 30% / 45%
Paladin's Shield	Paladin's Shield	25% (Only active above 25% life)
Endurance	Endurance Potion	10%
Ice Barrier	Frozen Turtle Shell	0    / 25% (When below 50% health)
Warmth	Warmth Potion	30% (Reduces damage only from cold-themed enemies)
Item	Source	Damage reduction bonus
Worm Scarf	Treasure Bag (Eater of Worlds)	17%

Armor Penetration

  Desktop/Console-Only Content: This section's information applies only to the Desktop and Console versions of Terraria.

Armor penetration is a statistic that reduces the defense of the player's targets. For instance, a Pixie normally has 20 defense. If the player has 5 Armor Penetration, then the Pixie will be taken to have 15 defense instead.

Source	Armor penetration bonus
Shark Tooth Necklace	5
Sharpening Station	4 for Melee Weapons only

Notes

It has been suggested that this page/section be rewritten. Reason: "Needs version separation: all info are  Desktop version only."

• The highest possible defense is 165 normally, and 173 in expert mode.
  • Chlorophyte Mask , Solar Flare Breastplate and Solar Flare Leggings or Vortex Leggings - 79 defense
  • Flesh Knuckles - 7 defense
  • Celestial Shell - 7 defense if worn at night
  • Paladin's Shield - 6 defense
  • Guarding with the Brand of the Inferno - 20 defense
  • Any other two accessories that give 4 defense at night - 8 defense
  • Warding modifiers on all accessories - 20 (24) defense
  • Ironskin buff - 8 defense
  • Well fed buff - 2 defense
  • The Dryad's Blessing grants an additional 8 defense.
  • Riding a Mechanical Cart at full speed gives an additional 7 defense (expert mode only, but can be imported to a normal world).
    • However, you cannot guard with the Brand of the Inferno while riding a Mechanical Cart.
  • Any sixth accessory that gives 4 defense at night, with a Warding prefix (expert mode only).
• The highest damage reduction is 73%.
  • Armor-based reductions are multiplicative.
    • Beetle armor with shell - 45% reduction
  • Accessory- and potion-based reductions are additive.
    • Frozen Turtle Shell - 25% reduction
    • Worm Scarf - 17% reduction
    • Endurance Potion - 10% reduction
  • This does not include the Paladin's Shield buff, since its damage reduction occurs before defense, and all others occur after defense.

 (100%-45%) * (100%-(25%+17%+10%)) = 26.4% damage taken = 73.6% damage reduction

Trivia

• Although not possible in-game, if a piece of armor were to gain a prefix, it would apply the effects just like an accessory would. For example, a set of Warding modified armor would add 12 defense total; each piece adds 4 defense to the total.
• If the player somehow has negative defense, they will constantly take 1 damage, and die with the death message "<playername> couldn't put out the fire".