Looking to mix my first liquid and using the calculator, I get the percentage (just put in the reccomended percentage from the vendor) but what do I do for drops per ml?
I really wouldn't recommend using drops per ml, it's not one bit accurate, but I guess that depends on how accurate you want to be, if it doesn't bother you then you'll be ok.
Tips comes in all sorts of different sizes, meaning more/less drops per ml compared to another bottle.
Either use syringes, measuring cylinders, or scales for accurate results.