It depends on a lot of different factors, including strength of
juice and voltage of battery.
With a regular e-cig and 24mg
juice, it's pretty close to 1:1, although maybe an analog has a bit more "kick" (I smoked unfiltered Camels).
With 36mg juice, or with 18mg at 6v on my Chuck, one good drag can make me dizzier than the first drag on an analog after 3 days without smoking.
Remember, the "dosage" in an e-cig isn't limited the way analogs are (e.g. per "cigarette"). You can have 2 or 3 puffs (or just one), or you can have more than a single cig but less than 2.
I'd suggest you start off just treating your e-cig like a regular cig, and learning how it's similar and different through experience. Some people count puffs, or keep track of
vaping time, but I just have some puffs until I feel satisfied, or feel like I've "had a smoke."