I smoke about 1 - 1 1/2 Marlboro Light 100's packs per day. What amount of nic mg should I get for my e-juice?
Take a look on your pack of Marlboro Lights - you will find the milligrams somewhere on it. It tells you the average mg per cigarette. I'm not sure myself but I think it is 0.7 for this brand (if it's different, substitute that number for the right number).
Take the total number of cigs per day... in your case around 35. Multiply by the strength. If that is indeed 0.7, that would be 35x0.7= 24.5 mg nicotine you would need per day with the liquid.
I would guess you would be using around 2 classic-carts daily (or liquid to that worth; or more carts if they hold less like if you buy a mini - but those all equal to around the same intake total, being around 2 ml liquid's worth) - so that means you should be good at 24.5 divided by 2, so around 12.25 mg (= 12.25 mg per ml liquid). Which isn't available, so you have to get as close to that as you can.
I would advise to go for 11 mg strength; but also buy some cartridges or liquid that is one step higher - use that one, just for ten minutes before going back to your 'standard', for any hard moments you encounter (like that famous first smoke of the day, or after a meal - whenever craving sets in without your standard strength being able to satisfy you, use the higher step for a bit...) but go back to the lower as soon as the craving gets satisfied, so after ten minutes or so - don't go and get used to the higher nicotine else you will be going higher and higher, while you wánt to go lower over time, probably...