You work the calculators by inputting variables. Say you have 100 mg/ml nic, and you want to get to 18 mg/ml, you will put the 18 in your "target mix" and it will tell you how much nic base you need to add, then you can add flavor percentages (it will also show as drops) PG/VG etc. So if you want 50/50 PG/VG, the calculator will take your nic base (in either PG or VG whatever you bought) and tell you how much more PG to add and VG. So you'll wind up with say 120 ml (I would suggest starting your mixes as 10 mg mixes to see how you like the flavors) of 18 mg nic, with whatever percentage of flavors you have chosen, along with how much VG and PG to add. I know it sounds complicated, but just start playing around with variables and it gets easier. If you try to make an "unvapable" mix by adding in the wrong things, the calculator will tell you. It's pretty simple if you just input what you WANT (the target) and then it should give you amounts as you start adding in variables. I'd highly suggest playing with one and it should become more clear
Anna