All new vapers are familiar with the confusion. When you go to buy your usual 12 mg/ml nicotine level, you can’t find that option there. Instead, e-juice comes with either 0%, 0.3%, 0.6%, 1.2% or 1.8% nicotine. So what should you do? What is the difference between nicotine strengths stated in mg/ml and those stated as percentages? How do you convert from one unit to another?
Nicotine Strength in mg/ml
Nicotine strengths are most commonly stated in mg/ml, which stands for milligrams per milliliter. This means that each milliliter of e-liquid in the bottle contains the specified amount of nicotine.
In the case of a 6 mg/ml e-juice, this means that each milliliter contains 6 mg of nicotine. If you need to calculate the total amount of nicotine in a bottle or tank, simply multiply the strength in mg/ml by the number of milliliters you have.
For example, if you fill a 5 ml container with 6 mg/ml e-liquid, you have 5 ml × 6 mg/ml = 30 mg of nicotine in your container. Similarly, a 10 ml bottle of 6 mg/ml e-liquid contains a total of 60 mg of nicotine.
Nicotine Strengths as Percentages
Nicotine strengths expressed as percentages are very similar, but a little easier to understand. Instead of combining a mass (in mg) and a volume (in ml), percentages use volumes for both. In simple terms, figures such as 0.3% or 1.8% only indicate how much of the liquid in the bottle is nicotine.
This means that if you have e-liquid containing 1.2% nicotine, every desired amount will consist of 1.2% nicotine and 98.8% PG, VG and flavorings.
Technically, this measurement is called "nicotine by volume", in the same way that the percentages on a bottle of spirits are called "alcohol by volume", abbreviated ABV. "Nicotine by volume" is sometimes also abbreviated NBV.
You could also calculate the percentage based on mass, if you wanted to, but e-juice manufacturers generally do not do it that way. We use ml, so they do too.
Converting from mg/ml to Percentage and Back
Converting from a nicotine strength in mg/ml to a percentage is very easy. You only need to divide the amount in mg/ml by 10. So if you have 6 mg/ml e-juice, this corresponds to 0.6% e-juice. 18 mg/ml e-juice corresponds to 1.8% e-juice. And if you have high-strength 72 mg/ml nicotine base, that becomes 7.2%.
The conversion could not be simpler. To convert back from a percentage to mg/ml, simply multiply it by 10.
More Details on Combining Weights and Volumes.
Practically speaking, this is all you need to know to safely switch between percentages and mg/ml values. But if you are interested in knowing exactly why it works this way, here is some more information.
The problem is a little complicated because values in mg/ml combine mass and volume. The practice originated in China, where the first e-cigarettes were manufactured. This would not pose a problem, but to calculate a percentage, you need to use two volumes, not one volume and one mass.
To calculate it yourself, you need to know how much volume each mg of nicotine occupies in liquid form. Nicotine has a density of 1.01 grams per cubic centimeter, which means that 1,010 mg of pure nicotine occupies one milliliter. We can use this to convert mg of nicotine into ml of nicotine.
First, we need to find the total amount of nicotine under consideration, in mg. As mentioned earlier, you simply multiply the nicotine strength – for example, 6 mg/ml – by the bottle size – for example, 10 ml. So in this case we have 60 mg of nicotine. Given the density of nicotine, this amounts to approximately 0.059 ml of pure nicotine.
So to calculate the percentage, divide the volume of nicotine by the total volume of the e-liquid and then multiply the result by 100. This means that a 10 ml bottle of 6 mg/ml e-liquid contains (0.59 ml/10 ml) x 100% = 0.59% nicotine. Since we do not need to be that precise, it would be stated on the bottle as 0.6%.
You will not actually need to do this, but it explains why all you need to do is divide by 10 to convert from mg/ml to percentage. Nicotine has a density similar to that of water, essentially 1g per ml, and this makes the calculation really simple.
Congratulations: You Will Never Order the Wrong E-Juice Again
If you are not too traumatized by the improvised math, you can now confidently explain what mg/ml means, what the percentage values for e-liquids mean and easily convert between them. No matter where you order from, you know exactly what you are getting.
