One of the biggest problems people have when switching to e-cigarettes is not knowing the nicotine ratio between e-cigarette and conventional cigarette. Most smokers don't even know how much nicotine they consume on a daily basis. They measure it with the numbers of cigarettes. When switching to e-cigarettes, minimize the possiblity of taking in more nicotine than the amount you were accustomed to.
The calculations are solely based on the nicotine contents of e-Juice and cigarettes. There are few other difficult to measure factors to consider, such as the number of cigarette puffs, e-Juice nicotine quality and how the body absorbs nicotine using e-cigarettes vs conventional cigarettes. However, the calculations are reasonable estimates.