Battle formulas — decompiled from FF8_EN.exe

Battle formulas — decompiled from FF8_EN.exe

Exact integer arithmetic as compiled in the PC executable (function addresses given; image base 0x400000). Where the code differs from commonly circulated formulas, the difference is flagged. Notation: rand255 = uniform 0..255, randVar = rand%33 + 240 (the ±6% damage variance factor, applied as dmg × randVar / 256).

Character stats (`Stat_ComputeCharaStat` 0x496440)

Kernel growth curve bytes A, B, C, D per stat; J_val = junctioned magic’s junction value, count = magic quantity (0–100):

STR/VIT/MAG/SPR: stat = weaponBonus(STR only) + (C + lvl·A/10 + lvl/B − (lvl²/D)/2)/4 + savedBonus + J_val·count/100, capped 255
SPD/LUCK: stat = bonus + lvl·A + lvl/B − lvl/D + savedBonus + J_val·count/100 (no /10, no level², no /4)
Max HP (0x496310): HP = savedBonus + C + lvl·A − 10·lvl²/B + hpJ_val·count — ⚠ the HP junction term has no /100 divisor
HIT (0x4967C0): weapon.attackParameter + hitJ·count/100; EVA (0x4968A0): SPD/4 + evaJ·count/100
All stats are then scaled by the Stat+X% ability multiplier (× mult/100, base 100); HP caps at 9999.

Monster stats (0x48C1C0 / 0x48C3F0 / 0x48C500)

From the .dat info_stat 4-byte curves: STR/MAG = (C + lvl·A/10 + lvl/B − (lvl²/D)/2)/4; VIT/SPR/SPD/EVA = C + lvl·A + lvl/B − lvl/D; each is then scaled by the AI-controllable stat variable (× var/10), capped 255. HP = HP1·lvl²/20 + (HP1 + 100·HP3)·lvl + 10·HP2 + 1000·HP4.

Physical damage (`Damage_ComputePhysicalCore` 0x492C40)

dmg = [ P × ((265 − VIT) × (STR + STR²/16) / 256) / 16 ] × randVar / 256

Vit 0 sets VIT = 0. Hit roll (0x492BA0): 255×(HIT + LUCK_atk/2 − EVA_tgt − LUCK_tgt)/100 ≥ rand255 (attacker Darkness quarters HIT); Sleep/Stop on target or accuracy 255 = auto-hit. Crit roll (0x492B30): LUCK + critBonus ≥ rand255 → damage ×2. Modifiers (0x48F600): Protect ÷2, back attack ×2, zombie target ÷2, Defend ÷2; attack element: dmg += dmg × elem% × (800 − elemDef)/10000.

Gunblade (0x48F480): dmg = [(CRIT_BONUS/20 + 2) × 4·P × ((265−VIT)×(STR + STR²/16)/256) / 128] × randVar/256; the trigger gives a flat ×1.5-style boost via that leading term and no crit roll happens.

Magic damage (`Damage_ComputeMagicAndGF` 0x491AD0)

dmg = [ P × ((265 − SPR) × (P + MAG) / 4) / 256 ] × randVar / 256

⚠ Enemy-cast magic is halved: if the caster slot is ≥ 3 (a monster), dmg >>= 1 — confirmed in the PC code. Shell ÷2, Defend ÷2. Element: dmg × (900 − elemDef)/100 where 800 = neutral (so 100 % absorb → negative); a zombie target treats Holy at 700 (×2). Drain spells heal dmg × (acc − drainResist)/100, inverted on zombies. Cap 9999.

GF damage (same function)

dmg = [ (SumMag+100)/100 × Boost/100 × P × ((265−SPR) × (LvlMod·GFLvl/10 + P + PwrMod) / 8) / 256 ] × randVar/256

SumMag = SumMag+% ability, Boost = boost value (up to 250). Diablos instead does GFLvl × maxHP / (PwrMod − LvlMod + 100); Demi does P × curHP/16.

Healing

Cure line (0x493280): heal = P × randVar × ((P + MAG)/2) / 256. Item in battle: 50 × P. White Wind: caster’s maxHP − curHP. Revive: target maxHP/8 (from item Med data: maxHP/4). Angelo Recover: P × maxHP/16.

Status attacks (`Battle_ApplyStatusWithResistRoll` 0x48F9F0)

chance = accuracy + atkStat/4 − tgtStat/4 − mentalResist (must be > 0; resist ≥ 100 = immune). Accuracy < 250: succeed when 255·chance/100 ≥ rand255; accuracy 250–254: automatic unless resist zeroes it; accuracy 255: bypasses the resist check entirely (rarely documented).

Specials

Formula	Code
Kamikaze	`5 × attacker maxHP`
Everyone’s Grudge	`P × character NumKills`
LV Up/Down	`newLvl = clamp(P×lvl/8, 1, 100)`, gated by `acc > rand255`
Devour	success when `atkHP ≥ tgtHP` and `rand255 ≤ 255×(atkHP−tgtHP)/atkHP`; heal `HPHeal × maxHP/16`
Card	success when `256 − 255×curHP/maxHP ≥ rand255` (≈1/256 at full HP, never 0 below max); rare card when `rand255 < 16`
Draw quantity	`((atkLvl − tgtLvl + 10)/2 − drawResist + rand(1..32) + MAG)/5 − stockAmount`, clamp 0–9
Draw-cast damage	`dmg × (rand255 + 10)/150`
Mug	success when `rand255 ≤ MugRate + SPD/2`
Drop/Mug slots	weights 178/51/15/12 (community docs often say /1 — the last slot spans rand 244–255)
Rare Item bug	with Rare Item, the 4th-slot compare compiles to `rand ≥ 261` — impossible for a byte, so weights become 128/114/14/0
EXP	`(damage share of HP) × (5·Exp·enemyLvl/avgPartyLvl − Exp)`, clamp 1..60000; killer gets the same with own level; Card/Devour/Doom kills give 0
GF XP	character XP / number of junctioned GFs; compatibility per cast: `+= tableByte − 100`, clamped 1000..6000
Multipliers	Darkside ×3, Angel Wing ×5, Berserk ×1.5, Cover ÷2; damage cap 9999 (60000 with Break Damage Limit flag)

Notable code-vs-community differences

Enemy magic ÷2 is real and unconditional for caster slots ≥ 3.
Drop/mug fourth slot weight is 12, not 1.
Rare Item makes the rarest slot unreachable (rand ≥ 261 bug).
HP junction is hpJ × count with no /100.
Crit chance is exactly (LUCK + bonus)/256 — the compiled 255·x/255 is a no-op.
Status accuracy 250–254 vs 255 behave differently (auto-success vs full resist bypass).

Key functions: Damage_DispatchByAttackType 0x4922B0 · Damage_ComputePhysicalWithHitCritRoll 0x492E10 · Damage_ApplyPhysicalModifiers 0x48F600 · Battle_RollDropItem 0x486650 · Battle_RollMugItem 0x4867C0 · Battle_ComputeDrawQuantity 0x48FD20 · Battle_RollCardCommand 0x48FBA0 · Battle_ComputeExpDistribution 0x494D40 · Stat_RefreshCharaBattleStats 0x495960.

Two ID spaces: command type vs attack type

An action carries two independent IDs, easy to confuse:

Command type (commandType, byte +1 of each BattleTask68Data action slot; the live copy is CURRENT_COMMAND_TYPE_ID at 0x1D27AD9). This is the command — Attack, Magic, GF, Item, Mug, Darkside, and the synthetic gunblade/Renzokuken variants. It selects animation, on-hit text and recoil behaviour, not the damage formula. (This field was mislabelled commandTypeWIthGunblade in an earlier pass — it holds the plain command type; the gunblade logic only reads it.)
Attack type (p_attack_type, from the kernel Attack Type field of the magic/ability). This is what Damage_DispatchByAttackType (0x4922B0) switches on to pick the damage formula.

Attack-type → formula dispatch (`Damage_DispatchByAttackType`, 0x4922B0)

Attack type	Damage function	Notes
Physical attack	`Damage_ComputePhysicalCore(…,0)`	hit + crit roll first
Magic attack	`Damage_ComputeMagicAndGF` (unmissable)
Magic ignoring target SPR	`Damage_ComputeMagicAndGF` (ignore SPR)
GF	`Damage_ComputeMagicAndGF` (GF)
GF ignoring target SPR	`Damage_ComputeMagicAndGF` (GF, ignore SPR)
Percent magic damage	`Damage_ComputeMagicAndGF` (% current HP)	Demi
Percent GF damage	`Damage_ComputeMagicAndGF` (Diablos)
Squall gunblade attack	`Damage_ComputeGunblade`
Renzokuken finisher	`Damage_ComputePhysicalCore(…,0)`
Percent physical damage	`Damage_ComputePhysicalCore(…,1)`
Kamikaze	`Damage_ComputePhysicalCore(…,3)`	5 × attacker maxHP
Everyone’s Grudge	`Damage_ComputePhysicalWithHitCritRoll(…,16)`	× NumKills
Physical, ignore VIT	`Damage_ComputePhysicalWithHitCritRoll(…,19)`
Curative magic	`Damage_ComputeCurativeMagic(…,7)`
Curative item	`Damage_ComputeCurativeItemSpecial(…,14)`
White Wind	`Damage_ComputeCurativeItemSpecial(…,9)`
Angelo Recover	`Damage_ComputeCurativeItemSpecial(…,15)`	give % HP
Revive / Revive at full HP	`Damage_ComputeReviveHP` / resurrection
Fixed / target HP−1 / GF-level fixed / 1 HP	`Damage_ComputeFixedSpecial(…,11/12/13/18)`
LV Down / LV Up	`computeLvlUpDown(…,0/1)`	LV Up also restores HP
Scan	scan flag + text	sets abbreviated-repeat flag
Card	eject + card-obtained text	miss if no card
Devour	HP-ratio success roll
Angelo Search	random item find
Moogle Dance (Moomba)	GF revive

Before the switch, sleep/confusion are cleared on the target (unless the attack is a medicine item or shelled magic); after it, back-attack status is cleared.

The command-type ID space (complete)

Battle_applyDamage (0x48FE20) dispatches on commandType twice via two-level jump tables (cmp id, 0xFE; ja default): stage 1 (0x48FF2F, damage-formula fields) through BATTLE_COMMAND_SWITCH_REMAP1 (0x491250), stage 2 (0x49043B, semantic handler) through BATTLE_COMMAND_SWITCH_REMAP2 (0x4913B8). The IDs fall into two disjoint bands.

Real kernel battle commands (0x00–0x26) — indices into the kernel battle-command ability list:

ID	Command	ID	Command	ID	Command
0x00	none / Kamikaze / Phoenix Pinion (fail sentinel)	0x0E	Shot (Irvine)	0x1A	Recover
0x01	Attack	0x0F	Blue Magic (Quistis)	0x1B	Revive
0x02	Magic	0x10	Slot (Selphie)	0x1C	Darkside
0x04	Item	0x11	No Mercy (Seifer)	0x1D	Card
0x05	Renzokuken launch, no finisher	0x12	Sorcery (Edea)	0x1E	Doom
0x06	Draw	0x13	Combine (Selphie “The End”)	0x1F	(unknown 0x1F)
0x07	Devour	0x14–0x16	Slot/No-Mercy/Sorcery item variants (base \| 0x04)	0x20	Absorb
0x08	Monster attack	0x17	Defend	0x21	LV Down
0x0B	Zell Duel link (launch)	0x18	Mad Rush	0x22	LV Up
0x0C	Mug	0x19	Treatment	0x26	MiniMog
0x0D	Item sub-link

Synthetic pseudo-commands (0xEC–0xFE) — injected at runtime for the multi-stage limit and gunblade sequences (0x27–0xEB, 0xF2, and 0xFF are unused and route to the generic handler):

ID	Command	Character / mechanic
0xEC	Seifer link	Seifer
0xED / 0xEE	Shot on-hit / expire	Irvine
0xEF	Zell Duel link (secondary)	Zell
0xF0	Angelo auto-move	Rinoa
0xF1	Duel (main)	Zell
0xF3	Darkside + gunblade trigger	Squall/Seifer
0xF4	Angelo / Chocobo (Invincible Moon…)	Rinoa
0xF5	Odin / Gilgamesh	GF
0xF6	Doom countdown reached 0	—
0xF7	Reflected-spell variant	—
0xF8	Mug + gunblade trigger	Squall
0xF9	Renzokuken finisher (Rough Divide … Lion Heart)	Squall
0xFA	Renzokuken launch / sequence marker	Squall
0xFB	Renzokuken on-hit (each initial hit)	Squall
0xFC	Special action (generic)	—
0xFD	Gunblade on-hit (Attack + trigger)	Squall
0xFE	G-Force (GF summon)	GF

The gunblade variants (0xF3/0xF8/0xFD) and the Renzokuken launch pair (0x05/0xFA) collapse to shared handlers in stage 2; the gunblade forms are produced by Battle_ApplyGunbladeTriggerHit (0x485160) from the base command in commandType. computeDamageEndOfAction (0x484180) then queues Darkside’s self-damage recoil after a Darkside hit (0x1C or its gunblade form 0xF3) via the internal command 0 — the same path as the poison end-of-turn tick.