## Foreword

The information found in the guide are based on a great document created by arkkus#4630 and you can find the original here.

## Damage formula

The damage formula in Honkai: Star Rail is almost the same as the one in Genshin Impact - which isn't that surprising as Star Rail copies a lot of systems from Genshin. So, here's how the damage formula looks like:

Let's go over the 7 factors that influence the final damage.

##### Base DMG

To find the Base DMG value you need to use another formula:

###### Base DMG = (Skill Multiplier + Extra Multiplier) * Scaling Attribute + Extra DMG

Where:

• Skill Multiplier = this is the percentage value you can find in the skill description (Deal DMG qual to XX%),
• Extra Multiplier = this appears only on some skills, like Dan Heng's Ultimate that deals additional damage to slowed enemies,
• Scaling Attribute = this is the attribute the skill scales off - in most cases it's ATK,
• Extra DMG = this is the flat additional damage that appears on some skills.
##### DMG% Multiplier

All DMG% is added together and grouped into one place in the DMG equation. The equation is as follows:

###### DMG% Multiplier = 100% + Elemental DMG% + All Type DMG% + DoT DMG% + Other DMG%

Remove DMG% multipliers if they are not relevant to the calculation. For example, if Hook has 38.9% Fire DMG and gains 20% DMG against a Burning/Bleeding enemy from “Woof! Walk Time!” then her total DMG% multiplier is 158.9% against a Burning or Bleeding enemy, but only 138.9% against a non-Burning or Bleeding enemy.

##### DEF Multiplier

DEF Multiplier scales with the level difference between characters, similar to Genshin Impact. The higher the attacker level compared to defender level, the greater the DEF Multiplier. The DEF related equations for a normal defender are:

###### DEF Multiplier = 100% - [DEF / (DEF + 200 + 10 * Attacker Level)]

To find the DEF, you need to use another formula:

###### DEF = Base DEF * (100% + DEF% - (DEF Reduction + DEF Ignore)) + Flat DEF

DEF cannot go below 0.

##### RES Multiplier

The RES Multiplier operates by the following equation:

###### RES Multiplier = 100% - (RES% - RES PEN%)

All enemies appear to have a base 20% RES to all elements unless they have innate weaknesses or resistances. If an enemy is weak to an element, then they have 0% RES to that element. If an enemy is resistant to an element, then they have 40% RES to that element.

RES cannot go below -100% or above 90%.

##### DMG Taken Multiplier

This portion of the equation functions differently from Genshin Impact, where it would normally be a part of DMG%. In Honkai: Star Rail, the DMG Taken Multiplier operates by the following equation:

###### DMG Taken Multiplier = 100% + Elemental DMG Taken% + All Type DMG Taken%

Example sources that affect this multiplier include Welt’s Ultimate as well as Sampo’s Ultimate. This multiplier cannot go above 350%.

##### Universal DMG Reduction Multiplier

This portion of the equation is as follows:

Universal DMG Reduction Multiplier = 100% * (1 - DMG Reduction_1) * (1 - DMG Reduction_2) * ...

When an enemy has Toughness, they have 10% Universal DMG Reduction, which is reduced to 0% when broken. Note this multiplier stacks multiplicative with other sources.

##### Weaken Multiplier

The Weaken Multiplier is related to the Weaken status effect that can be applied by Natasha and Sampo’s passive Trace. At present, it is only applicable when calculating enemy damage, but may be relevant in the future if enemies can inflict Weaken:

Weaken Multiplier = 100% - Weaken%

## Calculating damage

Now that all the factors of the damage formula are explained, we can accurately calculate damage against same-level enemies.

Let's use Tingyun as our test subject - here are her stats: Now let's list everything that affects the final damage:

• 1062 ATK
• 25.8% Lightning DMG
• 4p Musketeer: +10% Basic DMG
• Lvl 2 Basic Skill Multiplier: 60%
• Lvl 50 Tingyun against Lvl 50 enemies: 50% DEF Multiplier
• Enemy is not weak to Lightning: 80% RES Multiplier
• Enemy is not affected by any DMG Taken debuffs: 100% DMG Taken Multiplier
• Enemy is not broken: 90% Toughness Multiplier

And now it's time to input those number into the damage formula above: It matches!

Now let’s try against this enemy when they’re broken, which changes the Toughness multiplier to 100%. It matches again!

Now let’s try against an enemy weak to Lightning, which changes the RES multiplier to 100%. Welp, we're off by 1. That's most likely caused by a rounding error as the character's attributes values are displayed as integer.

Let's use another character now - here are her stats: Now let's list everything that affects the final damage:

• 1432 ATK
• 18.6% Quantum DMG (15.6% from Planar Sphere, 3% from Traces)
• She's under the effect of Last Tile Claim buff(S2) which gives +15% DMG (this is considered All Elemental DMG% by the game’s calculation)
• 4p Musketeer: +10% Basic DMG
• Lvl 3 Basic Skill Multiplier: 70%
• Lvl 50 Qingque against Lvl 50 enemies: 50% DEF Multiplier
• Enemy is not weak to Quantum: 80% RES Multiplier
• Enemy is not affected by any DMG Taken debuffs: 100% DMG Taken Multiplier
• Enemy is not broken: 90% Toughness Multiplier It matches again!

Now let’s try against an enemy weak to Quantum, which changes the RES multiplier to 100%. And it matches again!

The document linked at the top of the page has more examples in case you need more.

## Stats

While calculating the stats of a character, you need to know that the formula works a bit different than in other games - the 'bonus' stats you're getting from Light Cones are actually combined with the base stats of the character and only then other increases are applied.

• HP Total = (Character Base HP + LC Base HP) * (1 + HP%) + Flat HP
• ATK Total = (Character Base ATK + LC Base ATK) * (1 + ATK%) + Flat ATK
• DEF Total = (Character Base DEF + LC Base DEF) * (1 + DEF%) + Flat DEF
• Speed Total = Character Base Speed * (1 + Speed%) + Flat Speed