OA/DA to calculate your ETH?

[tqFan]

I used the first one from the official guide in the calculator and it matches in-game values so it must be correct.
It can be simplified to the following form

v.pth = Math.max((v.oa - v.da)*(0.02275 + 140/(7*v.oa + 2*v.da)) + 90, 60)

Max was used because PTH cannot be lower than 60:

Note that PTH cannot go below 60 for you or your enemies, meaning that no matter how much Defensive Ability you or your foe may have, you will never have a lower than 60% chance to hit them, and vice-versa.