Hi John!
I just started dabbling in DIY over the past couple of weeks. Here's one of the calculators to which b.m. may have been referring:
eJuice Me Up - Best eJuice Calculator I'm glad I never became a chemist/chemical engineer because I'm not one who's about 100% precise measurements
I have 50/50 36mg unflavored nic (for when I want a little "zoosh" in my
juice.) I got a quart of PG and a quart of VG and have already split those into 50/50 bases. Now, I just use either pipettes or the flavor's bottle dropper and sort of wing it. I'm not doing complex flavors or combinations, but I'll at least make note of how many drops of each flavor and with what dropper I used (i.e. the bottle tip, my 1mL pipette or my 3mL pipette - not all drop sizes are the same) I just eyeball the "rest" of the 10 mL in my bottle (knowing there's always some headroom at the top.)
I generally mix everything at 0 nic, as I've seen some of my premade juices discolor and even get a little funky tasting if they sit too long. I basically add a few drops of my 36mg nic base on a tank-by-tank basis
I'm not hell-bent on an "exact 50/50 mix, taking into account that my flavors are PG based" or exact "percentages" of flavor in the mix (hence, glad I'm not a research chemist
) If it tastes good, then it's a good batch.
I use the calculator to track my notes on each mix. Then I have a reference point for the next time I want to redo one.
It's fun - I've browsed through a number of recipes, trying to find things that might sound good. It's all experimentation.
Best wishes!