Thornmail is proven to shut down physicals hardcore but now there's math that shows just how much it shuts physicals down.

Formula:

(1-A/A+100)*D*LS=D*(.3*(1-MR/MR+100)


Legend:

• A=opponent armor
• D=Your damage
• LS=Your lifesteal
• MR=Your magic resist

How to use:
Simply add in your opponents armor your magic resist and your current damage and you will see how much lifesteal u need to break even on your own damage from thornmail.


Conclusion:
Doing some quick and easy numbers 25% armor requires 40% lifesteal to penetrate 50% armor requires 60% alright this seems reasonable sort of now watch this 75% requires 120%. This 75% is the tank. This means that unless u manage to get 120% lifesteal u can't ever touch the tank EVER. If you do you will never win. Now applying some fancy additions you can further determine the extent of the damage if you fall short of meeting the expected LS.(yes this is just shifting around the original formula to show what numbers are left)

Second formula:

D*(.3*(1-MR/MR+100)-(1-A/A+100)*D*LS = Damage taken

How to use:
plug in all the numbers and see what you get.

Note: I am not calling thornmail OP but I am saying it's too good a shut down on physicals.Also note that getting 5 fully charged Blood Thirsters will cause you to actually fight back against a rammus to some extent so might want to try that out when the game has lasted 2 hours.

edit: Apparently pressing enter instantly posts your topic and i can't change the name back to thornmail after accidentally deleting the T ><

Out of curiosity where did you get that formula? And interesting math.

After trying to freakin figure out how to counter thornmail i sat down and wrote a few equations. They aren't too complicated but i thought i'd share them

Such a shame that Lifesteal isn't even remotely the counter to Thornmail, but nice math. Try out some Magic Resistance or Armor Penetration. It should destroy any threat of Thornmail.

This. I'd be interested to see how the math works out though.

feel free to use the equation to plug in numbers and see if u can manage to break through thornmail )

Mmmmm.... If you see the enemy go Thornmail grab things like SotD and Hexdrinker/Wit's End

It might not be what you WANT, but it's better than dying >.>

Exactly what MR value did you use for yourself? We can understand that AD value doesn't matter for this break point, but since MR directly affects the damage you take without affecting the lifesteal value, this is important data.

plug in the numbers i gave a formula

Sat down and worked out the numbers.

• Base MR ~ 30 MR
• Negatron Cloak +48 MR
• Stark's +20 ArPen +20% LS
• Last Whisper +40% ArPen
• Bloodthirster (Full Charge) +25% LS

Brings you within a hair of breaking even against 300 Armor. Total cost: 8780 G.

More than 2000 G? Yep. But they had to get 300 Armor so they spent at least another 1000 G on armor.

Those items all help you do your job as an AD champ anyways, where only a few champs get offensive benefits from Armor (Rammus, Malphite... anyone else?). Everything except the cloak is straight offense. You got total immunity to Thornmail plus a lot of damage dealing (+140 AD, +40% AS, +40% ArPen, +20 Arpen ), and unless their whole team has Thornmails and 300 total Armor you'll gain health against them.

FYI: If you count standard MR (~30), it only takes 100% LS, not 120%, to break even against 300 Armor w/ Thornmail. You only need 120% if you have zero MR. That's still 4 Bloodthirster's, of course. But why counter it that way when you can do it for 4000 G less?