I wouldnt worry about it too much. Just look at the websites and if possible, get a drug calc book. I did this the summer before I started classes, and I passed my Drug Calc exam on the first try with a 95% *(we have two chances to pass with 95% or you dont get to pass meds in clinical). I found that the proportion/ratio method worked best for me. I just got an older version book and worked through it cover to cover.