When making DIY e-juice, you don't have to use nicotine. However, if you are an ex-smoker, you might prefer a certain concentration of nicotine, to quench your thirst for nicotine. Note that between 0-24mg nicotine, there is no good or bad nicotine concentration, if you do not go overboard. A good rule of the thumb is to measure 8-11mg of nicotine if you were a light smoker, 12mg to 16 mg for regular smokers, and 17mg to 24mg for heavy smokers. Knowing your nicotine level is very important. Besides, nicotine is very strong and if in excess it could lead to a throat irritation, which is a very unpleasant experience.
To accurately measure the level of nicotine, you can use any of the online e-juice ingredient calculators. However, if you don't have access to the internet, you can always use this formula:
Total amount =mg
Strength*volume=total nicotine amount
Assuming you is a moderate smoker preferring 16 ml concentration and you need to make 100ml of e-juice, here is a calculation of the amount you will need:
If you are using dilute nicotine 100mg/ml:
Note that we used 100mg/ml nicotine. This is because handling pure (100mg/ml) can be very dangerous; could even lead to death. Thus, it requires a professional to handle it.