How Penatration is calculated?

As Ele/Mes, using Air Skill, i don't get it when it says 25% Armor penatration ... can someone tell me wat does it trying to say? Show exp please

As I understand it, that 25% is a reduction against the target's effective armor - so it reduces their 60 armor to 45 armor.

These are the formulas I have for damage/armor:

Spells and spell weapons
damage = (base damage)*2^([3*Clvl - Effective_Armor]/40)

Non spell weapons
damage = (enhanced damage percentage)*(base_damage_mod + base damage)*2^({[71/15]*Weapon_attr - Effective_Armor}/40) + Extra_damage

These formulas are all well and good if a bit too involved for casual interest.. WHat I've always wondered when seeing them is where did the site get them. Is this something gotten direct from ANet? Or is it something some math wiz thinks they have figured out?

Actually that non spell weapon formula isn't exactly right. It's actually a piecewise function, with amounts over 12 using a different formula than amounts 12 and under...

But anyway, I'm pretty sure the equations that people have found are quite accurate...

As for armor penetration... against a target with little armor, 25% penetration probably makes your attacks 30% stronger. Against a target with very large armor, you could probably get as much as 80% added damage by piercing the armor...
rough estimates based on the equations, I didn't actually calculate it but it looks about right

I always figured that the % meant the chance for the attack to penetrate armor... but those formulas look important so I won't argue. Hehehe.
(For the record, I had the urge to make a bad joke on the title of this thread, but I restrained myself.)

Penatration is measured in inches.

-Witt78