After you figure out how much juice you are using per day, you might want to keep this in mind...
Some studies have shown we may be absorbing as little as 10% of the nicotine from
vaping.
And some here find flaws in those studies and think they may be getting as much as 40% of the nicotine from vaping.
So, for example...
Let's say you're using 18mg strength liquid, which is 18mg of nicotine per milliliter.
If using 3ml per day of 18mg strength liquid, you would theoretically be getting 54mg per day assuming 100% absorption.
But taking absorption rates into account you will only be getting anywhere from 5.4mg to 21.6mg of nicotine per day.
And that would equal anywhere from about 5 to 43 cigarettes.
Because the amount of nicotine absorbed from real cigarettes is anywhere from 0.5mg to 1.1mg, and some are even more.
So really it all depends on which cigarettes we are talking about, and how much we really absorb from vaping.