How are +% modifiers applied?

Let's say my merc uses a skill like Galvanic Shards that "converts #% of Physical Damage to Lightning Damage".

If you have gear or passive nodes increasing both - are they +%physical applied to your base physical damage and then converted to lightning? Or do the boosts only apply to the final damage? Meaning if you have skills that convert 100% to lightning, no +%physical applied at all?

Bonus question: are damage modifiers from jewels and such stacking? So if you equip multiple +% lightning via jewels, are they combined?

The best thing you can do with these kind of questions is to equip/unequip, spec/despec the relevant stat and see how that changes your dps numbers in the skill ingame

but to quickly answer, I believe in poe2 if you convert 100% then the original dmg(phisical) increase wont have any effect

And yes, all increse dmg from every source is added together and then multiplied for the calculation. This means you have diminishing returns in increase dmg

on the other hand more/less dmg is independently multiplied in the final calculation and for that reason is very powerful

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BlackForest10#0653 wrote:

The best thing you can do with these kind of questions is to equip/unequip, spec/despec the relevant stat and see how that changes your dps numbers in the skill ingame

Kinda hard to test as anything seems to affect many things at once. Hence me trying to clarify if for a build that mainly uses galvanic shards, +phys or +lightning would be best.