Can someone confirm if I understand crit damage correctly?

Assuming a critical hit is triggered, crit damage will deal damage equal to original damage multiplied by CDMG percentage ON TOP of the original damage, right?

Meaning if you have 250% crit rate, instead of X damage, you deal 3.5X.

I'm trying to calculate equivalent value for Phantom Touch, it's 5xATK but not subject to crit, and I'm trying to estimate the equivalent multiplier under different crit values. 

In other words, is 5xATK equivalent to 1.43xATK with 250% CDMG?