Mathwise it's about 6mg of nicotine adsorbed per cigarette. That gives you a way to compare dosage of nicotine to vaping a certain concentration of juice.

Probably not a great 1:1 because there are other things in play with smoking, but, ballparky enough.

If you wanted something closer, you'd need to figure out how the other compounds in cigarette smoke affect nicotine adsorption and activity.