EO2/Formulas

Detailed explanation of how Etrian Odyssey II: Heroes of Lagaard calculates damage, ailment/bind infliction, recovery, and so on. This also explains how various modifiers in the Skills pages impact gameplay.

Damage

$Damage=([ATK÷DEF\times 1.7]+var)\times Damage\mathrm{\%}\times Vuln\mathrm{\%}\times Buffs\mathrm{\%}$

• var is a random number from 1 to 5 if $(ATK÷DEF\times 1.7)<5$. Otherwise, $var=ATK÷DEF\times 0.17$
• Damage% is the Damage % of the skill being used. Treat normal attack as 100%.
• Monster attacks apply another ×0.8 multiplier to damage dealt.
• Vuln% is the target's vulnerability to the damage type. Neutral vulnerability treats this as a 100% multiplier. Resisted hits indicate lower than 100% vulnerability. 110% or higher vulnerability to a damage type is treated as a weakness to that damage type (and qualify for the Alchemist's Analysis passive). Immunity means 0% vulnerability.
• Buffs% is the combined effect of all passives, buffs, and debuffs between attacker and target. Treat buffs to attacker's ATK and debuffs to target's DEF as increases to damage dealt, and vice-versa.
  • Buffs and passives that provide increase to resistance is instead calculated as decrease to Vuln% and vice-versa, and are exempt from Buffs%.
• For physical/elemental hybrid attacks, perform the same damage calculation for each component separately, then take the average between both results. For example, a cut/fire hybrid normal attack against an enemy with 100% cut vulnerability but 50% fire vulnerability will, overall, do 75% the damage of a normal attack on the same enemy without the elemental imbue.

STR-based Attacks

$ATK=[STR+(WpnPower÷2)]\times (20+STR)\times (20+WpnPower)$
$DEF=(20+VIT)\times (20+ArmorDEF)$

• WpnPower is the ATK bonus from the weapon, divided by 3. Monsters don't use weapons so this is equal to their STR (DEF on Codex).
• ArmorDEF is the DEF bonus from your armor, divided by 3. Monsters don't use armor so this is equal to their VIT (DEF on Codex).

TEC-based Attacks

$ATK=[TEC+(SpellATK÷2)]\times (20+TEC)\times (20+SpellATK)$
$DEF=(20+attackVIT)\times (20+ArmorDEF)$

• SpellATK is equal to the Spell ATK listed in the respective skill, used by both the party and the enemies. If Spell ATK is not described, treat this as 0.
• Due to a bug in calculations the damage inflicted calculates off the attacker's VIT instead of the target's.
• ArmorDEF is the DEF bonus from your armor, divided by 3. Monsters don't use armor so this is equal to their VIT (DEF on Codex).

Hit Rate

$FinalHit=WeaponHit\times HitRate\mathrm{\%}\times \frac{1+(HitStat\times 0.01)+(attackLUC\times 0.005)}{1+(EvadeStat\times 0.01)+(targetLUC\times 0.005)}\times HitBuff\mathrm{\%}$

• For STR-based attacks, treat HitStat and EvadeStat as the attacker's and target's AGI respectively.
• For TEC-based attacks, treat HitStat and EvadeStat as the attacker's and target's TEC respectively.
• WeaponHit is a hidden value on the user's weapon. Most weapons have an innate accuracy of 100%, others with ACC modifiers will change this value. Monsters do not use weapons and treat this variable as 100%.
• HitRate% is the Hit Rate on the user's skill. Treat as 100% for normal attacks.
• HitBuff% compounds all Hit Rate and Evasion buffs/debuffs between user and target respectively. Treat an evasion debuff as a bonus to hit rate, and vice-versa.
• A head bind applies a ×0.8 multiplier, while a blinded attacker gets a ×0.2 multiplier. Both stack multiplicatively.
• FinalHit is then corrected to a minimum of 20% and maximum of 100%.

Critical Hits

$CriticalRate=5\times \frac{10+attackLUC}{10+targetLUC}$

• Critical Rate is corrected to a minimum of 1% and maximum of 50%.
• Critical hits only apply to normal attacks, and provide a ×1.25 multiplier to damage after all other calculations.

Action Speed

$BaseSpeed=\frac{AGI\times SkillSpeed\times WpnSpeed}{100}$
$BaseSpeed2=BaseSpeed+var1$
$FinalSpeed=BaseSpeed2+[random(0,12)]\times 2+1$

• var1 is a random variable between 0 to BaseSpeed × 2.
• SkillSpeed is the Activation Speed modifier of the skill you're using. Treat as 100% for a normal attack and for skills that do not mention an Activation Speed.
• WpnSpeed is the Action Speed multiplier of the weapon you're using, usually set at a minimum of ×1. Monsters don't use weapons and treat this variable as ×1.
• FinalSpeed is then corrected to a minimum of 1 if it is under that value.

Ailment/Bind Infliction

$Rate=Vuln\mathrm{\%}\times BaseRate\mathrm{\%}\times Health\times \frac{attackLUC+100}{targetLUC+100}$

• BaseRate% is the base infliction rate from the skill being used.
  • Any skill with infliction rate listed as 10000% is guaranteed to inflict the ailment/bind, skipping all further calculations, unless the target has an immunity to it.
• Vuln% is the target's vulnerability to the ailment/bind. Treat neutral vulnerability from regular enemies as 100%, 50% for FOEs and bosses.
• The Health variable is the multiplier from the Troubadour's Health skill.

Accumulative Resistance

These only apply for binds, not ailments.

• In Etrian Odyssey II: Heroes of Lagaard:
  • First apply a ×0.9 multiplier to Vuln%.
  • Apply a ×1.25 multiplier to Vuln% for each failure to inflict a bind, until the bind lands.
  • After a successful bind, remove all of the above multipliers, then apply a ×0.75 multiplier to Vuln% for that bind instead, repeating this multiplier for every additional time that body part was bound in battle.
• In Etrian Odyssey II HD:
  • For every failure to inflict the bind, add a flat 25% success rate, to a maximum of 90%. Remove these bonuses once the bind is successful.
  • After a successful bind, reduce Vuln% by 25%, to a minimum Vuln% of 5%. This vulnerability reduction does not stack, no matter how many times the same bind is inflicted to the target this battle.

Ailment/Bind Recovery

$Chance=BaseChance\times \frac{10+LUC}{3\times Level}+10\mathrm{\%}\times turns+Recovery$

• BaseChance varies on the disable:
  • Sleep, Paralysis: 40%
  • Panic, Fear: 30%
  • Poison: 25%
  • Everything else: 20%
• Each turn that passes after the disable is landed, adds an additive 10% chance of recovery.
• The Recovery variable is the bonus granted by the Troubadour's Recovery buff.

Healing

While healing in this game (slightly) uses the user's TEC, it uses a formula significantly different from how other games treat Healing Power.

$Healing=(BaseHealing\times \frac{160+TEC}{160})\times (1+Mastery\mathrm{\%})$

• BaseHealing is the Base Healing variable of the healing skill being used.
• Mastery% is the bonus given by the Medic's Healer skill or the War Magus's War Lore skill.

Preemptives and Blindsides

$PartyRating=(highestAGI+10)\times (highestLUC+10)$
$EnemyRating=(highestAGI+10)\times (highestLUC+10)$
$PreemptiveChance=5\times PartyRating÷EnemyRating+Ambush$
$BlindsideChance=7\times PartyRating÷EnemyRating-Sagacity$

• If a specific enemy formation is a guaranteed blindside, or if an FOE catches the player from behind, the battle starts with the party blindsided, bypassing all checks that would avoid it.
• If the party engages a boss or FOE from behind, they will get a guaranteed preemptive round, unless overridden by an enemy that causes a guaranteed blindside.
• PartyRating and EnemyRating each use the highest AGI and LUC stats among all combatants on the respective side.
• Ambush and Sagacity refer to the bonuses from the Survivalist skills Ambush and Sagacity respectively.
• PreemptiveChance is rolled first, and if successful, bypasses the blindside check.
• Both PreemptiveChance and BlindsideChance are capped at a minimum of 1% and maximum of 25%.

Escape

$EscapeChance=(10\times \frac{AGI+LUC+5}{EnemyAvgAGI+EnemyAvgLUC+5})\mathrm{\%}+10\mathrm{\%}\times FailedEsc$

• EnemyAvgAGI and EnemyAvgLUC is the average AGI and LUC respectively among the total enemy formation, rounded down to the nearest whole number.
• Every failed escape attempt by a party member this battle adds an additive 10% to the next escape chance.
• Learning Esc Up adds 30 to the individual party member's EscapeChance.
• EscapeChance is capped at a maximum of 90%.

Difficulty Modifiers

In Etrian Odyssey II HD, apply these multipliers in addition to all the above.

Variable	Expert	Basic	Picnic
Damage Dealt	100%	120%	500%
Damage Taken	100%	80%	10%
Ailment/Bind Infliction Rate	100%	120%	200%
Ailment/Bind Vulnerability Modifier	100%	80%	10%
Party's Ailment Damage	100%	120%	500%
Enemy's Ailment Damage	100%	80%	20%
Healing Power	100%	100%	300%
Party Accuracy	100%	100%	120%
Enemy Accuracy	100%	100%	80%
Party Action Speed	100%	100%	200%
Preemptive Rate	100%	100%	200%
Blindside Rate	100%	100%	20%
Escape Rate	100%	100%	150%
Environmental Damage	100%	80%	20%
EXP Gain	100%	100%	150%

References

• GameFAQs guide on formulae