XC2 damage calculation

Xenoblade Chronicles 2 damage formula

Damage = ((AutoAttack * Attachment * JustRange * Stability) + TypeStat) * (DmgRatio/100) * (1 + CriticalPower) * (1 + ClassEffect) * IdeaLvl * (1 + AdditiveMultipliers) * (1 + CancelBonus) *(1 + DriverFusionCombo) * (1 + Element) * (ChainRatio/100)* EnemyDefense * BArtsDamageRev * BladeArtsRev

>AutoAttack
Auto-Attack stat of current Blade

>Attachment
Accessories like Sword Attachment. Specific weapon attachments are additive with Master Attachment. Clone weapon types only benefit from Master Attachment.

>JustRange (if in specific distance from enemy)
+20%. Each weapon has a specific range they need to stand in to receive this increase to auto-attack stat. Aegis is between 3 and 7 meters. No effect if closer than minimum range or farther than max. List of ranges: https://xenoblade.github.io/xb2/bdat/common/ITM_PcWpnType.htm

>Stability
Random multiplier that increases (maybe decreases too) your auto attack. Every weapon type + chip combo has a different multiplier. List of stability values can be found at https://xenoblade.github.io/xb2/bdat/common/ITM_PcWpn.html
If you ignore this stability when calculating damage you get the average damage between the low and high rolls for stability.

>TypeStat
Physical or Ether stat of driver depending on weapon type and art/special type.
E.g. Ether Cannon uses ether for auto attacks, Rex's Rolling Smash is an ether type Art.
Poppi QTpi's level I special is physical, and the other 3 specials are ether type.

>DmgRatio
Dmg Ratio of auto hit, Art, or Special.
Rolling Smash Lv 5 = 490
Damage ratios for specials are in the guidebook/datamine. Their ratios increase with each level of their related red skill in blade affinity chart.
In Max Affinity state Driver Arts and Blade Specials get their levels increased by 1 (max level 6), which increases their damage ratios.
Poppi QT's level I special starts at 300 ratio with skill level 1, skill level 5 is 460 ratio, and level 6 from Max Affinity is 480 ratio. Level IV special has 1150 ratio.
Multi-hit attacks divide the dmgratio into each of the hits, but the distribution of the ratio to each hit varies by the attack used.
Auto-attack ratios for first/second/third attack are 50/80/120. Decimation Cannon is the only weapon with different ratios and uses 60/96/144.

>CriticalPower
No crit = 0
critical = 1.25 * (1 + total critical damage increases from skills, AUX cores, and parts)
Legendary Optical Headband = +.50
Poppi Pinpoint Weakness V = +0.50

>ClassEffect
Passive effect of class determined by roles of equipped blades.
Boosts damage dealt ↑ = +0.10
Boosts damage dealt ↑↑ = +0.15
Boosts damage dealt ↑↑↑ = +0.20

>Idealvl
Gain 5% damage increase per idea level that matches the element of your current blade. Level 0 = x1 damage, level 10 = x1.5 damage.

>AdditiveMultipliers
Pretty much every conditional damage effect from skills, AUX cores, and accessories. Such as damage to specific enemy types, or when low hp, or at Max Affinity.

>CancelBonus
Total of cancel stage bonus and increased damage when canceling effects. Cancel bonus does not apply to blade specials.
First auto-attack cancel = +0.10
Second auto-attack cancel = +0.20
Third auto-attack cancel = +0.30
Combo Enhance, Bestial Pursuit, Imperial Pursuit = +0.20
Legendary Hi-Tech Eyepatch = +0.54

>DriverFusionCombo
Break = 0
Topple = 0.25
Launch = 0.50
Smash = 0.50
Fusion Combos apply a damage up bonus if a Blade Combo hits while a break, topple, or launch is active and the damage boost lasts until that specific driver combo stage runs out. Applying the next driver combo stage while a blade combo fusion effect is active removes the fusion damage bonus and instead only applies a time extension bonus for the blade combo stage.
Fusion stage is the stage of the driver combo + the stage of the blade combo. Launch (3) + Volcano (2) would be a stage 5 fusion combo.
2 Stage: Damage +50%, Effect time +10%, Party Gauge +10, Exp gained +40%
3 Stage: Damage +50%, Effect time +10%, Party Gauge +10, Exp gained +50%
4 Stage: Damage +75%, Effect time +20%, Party Gauge +15, Exp gained +60%
5 Stage: Damage +75%, Effect time +20%, Party Gauge +15, Exp gained +70%
6 Stage: Damage +100%, Effect time +30%, Party Gauge +20, Exp gained +80%
7 Stage: Damage +100%, Effect time +30%, Party Gauge +20, Exp gained +100%
The fusion combo damage increase adds to the driver combo's damage bonus. Break (0) + Aqua (blade combo 1) would activate the 2 stage fusion combo increasing all damage dealt to the enemy by 50% (x1.5).
Topple + Photon (BC1) + Gamma Ray (BC2) would add together like 0.25 + 0.50 + 0.75, applying two fusion combos to the topple, for a total damage increase of 150% more damage (x2.5). If you then launched while this fusion combo was active, your damage bonus would drop back down to launch's base value of 50% (x1.5).
Fusion combo up skills and aux cores add their percentage to each fusion combo triggered.

>Element
Opposite element = 0.20
Same/Resisted element = -0.20
Adenine Battle Wisdom 5 = +1.00

>EnemyDefense
Enemies have percentage physical and ether resist just like blade defense stats. Datamine has values for these, and they can be positive (damage reduction) or negative (damage increase) values. Tyrannotitan Kurodil for example has 30 physical resist and no ether resist. Blade specials with Pierce property ignore defense.
Check RstPower and RstEther columns: https://xenoblade.github.io/xb2/bdat/common/CHR_EnParam.html

>BArtsDamageRev (if special lvl 1-3)
Battle affinity has a multiplier to special damage ranging from 0.75 to 1.25 at max affinity. This does not apply to level IV special.

>BladeArtsRev
S rank levels of trust have a modifier to special damage, ranging from 1.0 at S to 1.6 at S+.