You got to a site, enter in about 3 different numbers in fields and press enter, all numbers from Eve itself, so no calculations done by you.
As well doing it yourself in excel, creating a document, setting up the tables and writing the rules for each to work out the answer.
EDIT: I should add, I rarely use the calculators anyway, you know, not being retarded, I can work out damage multipliers and stacking penalties in my head, only when wanting to know a bit more complicated things like working out dps do I use the calculator.
