I'm new to this forum. I also had a question about absorption, nic rates, etc. and did find the answers here at ECF. While the research is not yet complete or conclusive on this subject, the general working hypothesis is about a 50% absorption rate. That is the best estimate the experts can tell us at this time, though more studies are needed. I just read about this a day or two ago here in ECF, and can't put my finger on the article this moment, but it's here, it's very informative, and, as usual, the information is documented by several trusted studies. That being said, again, the experts are quick to point out that the conclusions are premature and require more studies.
For me, my body knows how much nicotine it craves and when it is satisfied. If you are not being satisfied, just up the nic level in the juice until you are. With certainty, the nicotine your body is absorbing is not a straight calculation, i.e., a pack of lights is 12 mg of nicotine but this is NOT equivalent to vaping a ml of 12 mg/ml e-liquid, though that it what I erroneously thought at first. Personally, I think the 50% absorption may be high. Regardless, my body knows when I've had enough, or not enough, and that is the only equivalency that really matters to me. The right amount is the amount that allows me to be analog free and satisfied with my vaping experience...forget any conversions...as we simply don't know the facts about them yet.
Nicotine is in our food chain, in cruciferous vegetables like broccoli, in spinach, etc. Everyone has nicotine in their bodies, because it's in many of our common, every day foods, and at moderate levels is not harmful to humans, and may even be helpful. The level that satisfies me, is probably pretty close to what I used before vaping, or so the experts say...is free of the more than 4,000 chemicals in analogs, with more than 100 of them known carcinogens. I've recently YouTubed many naturopathic doctors recommending e-cigs to replace analogs, without reservation. The information is out there. These same doctors say that no one has ever died of nicotine use (in this context, and excluding tobacco use) and that it's no more harmful than a cup of coffee. No one has ever proved otherwise. We would have definitely heard about that.