The Milligram is a unit of measurement for mass equal to a thousandth of a gram. A gram is equal to the mass of one milliliter, one thousandth of a liter, of water at 4 degrees C. The abbreviation for milligram is mg.
Converting the strength of your cigarettes to an equivalent e-liquid is not simple, the mg rating for cigarettes usually doesn’t refer to nicotine like it does in e-liquids, cigarette packets usually display the mg of tar in a cigarette and not nicotine. Most cigarettes contain around 12mg to 15mg of nicotine, of which around 1mg per cigarette is absorbed into your blood when you smoke. It has been a long held misconception among smokers that ‘lighter’ cigarettes contained less nicotine because of the lower mg rating on the pack, which led many to believe they could quit simply by working their way down the mg ratings and trailing off their nicotine intake slowly. This didn’t work because the nicotine stays about the same, they simply smoked less and less tar (still not a bad thing) meaning their nicotine addiction stayed the same.
Not containing tar to measure, most e-liquids display a mg measurement of the nicotine content on the bottle. Many e-liquids measure their nicotine content in mg/ml, some however measure nicotine content in the form of a percentage of overall volume. This would appear as “0.3% nicotine by weight” or “0.3% nicotine by volume” both of which equate to 3mg/ml of nicotine.