Ever wondered how much nicotine do I put in e juice?... Mixing nicotine shots doesn't have to be rocket science. It's now common to find e-liquid in standardised bottles from 60ml short fill's with 10ml of space to 120ml short fills with 20ml of space. The space left is intended for your nicotine shot.
To create a 3mg nicotine e-liquid with a 60ml short fill you will require a single 18mg nicotine shot.
To create a 6mg nicotine e-liquid with a 60ml short fill you will require Two 18mg nicotine shots.
To create a 3mg nicotine e-liquid with a 120ml short fill you will require Two 18mg nicotine shots.