Put into words, fluid with a nicotine concentration of 100 mg/ml has 100 milligrams of nicotine in each milliliter of fluid. 12 mg/ml fluid has 12 milligrams of nic in each milliliter of fluid. If you're looking to do some more advanced blending, or simply want to make life a little much easier when blending, a calculator can be important. Here's a few really terrific calculators you can make use of.
http://spencerxrox520.fotosdefrases.com/how-to-make-natural-vape-juice-in-the-house-without-nicotine