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Calculating PG/VG Ratio’s After Adding Nic Shots To A Shortfill Bottle

Richard Winter DIY E-Liquid Mixing Leave a Comment

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The intention of this quick guide is to explain and give an understanding, with examples, what the overall PG/VG ratio of a shortfill bottle is when a Nicotine Shot (Nic Shot) is added. At the end of this guide you will know how to calculate the PG/VG ratio of any shortfill bottle when any type of nic shot(s) are added.

The following few paragraphs give an overview of the ingredients that make up e-liquid and explain what a shortfill and nicotine shot are. We’ll also touch on what a nicotine shot calculator does and doesn’t do.

If you’re eager to find out how to work out the PG/VG ratios of your shortfill after adding nic shots then please jump directly to the 3 examples we’ve given.

If you don’t already know, there are 4 ingredients that make up our E-liquid:

  • Propylene Glycol (PG)
  • Vegetable Glycerin (VG)
  • Flavorings
  • Nicotine

Propylene Glycol and Vegetable Glycerin: are the two main ingredients that make up our e-liquid. PG is the thinner of the two liquids and provides the “throat” hit whereas VG is a thicker liquid that provides the vapor. Most e-liquids will use a combination of the two in differing ratios, typically 50VG/50PG, 70VG/30PG or 80VG/20PG.

Flavoring: is normally added to our e-liquid and comes in an endless amount of different flavors. These can be single flavors or a more complex combination of several flavors. Flavor concentrates are used when DIY e-liquid mixing whereas shortfill bottles are chosen and purchased for their particular flavor.

Nicotine: provides the stimulation and “Hit” when it’s added to e-liquid. Typically it’s used to stop the cravings when transitioning from smoking to vaping. Because of the TPD laws in the EU, e-liquid containing nicotine can only be sold in 10ml size bottles. Nicotine is normally sold at a strength of 18mg and comes suspended in PG, VG or a combination of both. This is what is called a “Nic Shot”.

Whether we are making our e-liquid from scratch (DIY) or using Shortfills, our overall aim is to know the flavor and nicotine strength of our e-liquid together with the ratio of PG against VG.

While this is straightforward and easily calculated when mixing our own e-liquid from scratch, knowing the exact ratios of our e-liquid after we’ve added nic shots to a shortfill bottle can be a little ambiguous to say the least.

DIY e-liquid mixing is not the topic of this guide as we have previously covered this in our other guides and of course we have a really good e-liquid mixing calculator which works out every percentage and ratio.

For reference, we have included links to our DIY e-liquid guides in you want to read further information on these topics:

However, our specific focus is to explain in detail how the PG/VG ratio of a shortfill bottle will change when we add a nicotine shot. How we can calculate the PG/VG ratio of a shortfill and what type of nic shot we can add in order to maintain our desired PG/VG ratio.

Before we delve into the calculations I must point out that even though we can change the PG/VG ratio of a shortfill bottle by adding nic shot(s), there are limitations. What we can do is to give you the tools to choose what the possibilities and options are.

What is a Nicotine Shot?


A Nicotine shot is a 10ml bottle of flavorless e-liquid suspended in either PG or VG, or a ratio of the two, designed to be added to nicotine free e-liquid. Although the maximum strength set by the TPD is 20mg/ml, the majority of suppliers opt for 18mg/ml as this makes the numbers easier to calculate.

What is a Shortfill Bottle?


Shortfalls are nicotine free e-liquid in varying PG/VG ratios with increased flavor percentages sold in a bottle that is “Short Filled” to allow enough space to add your Nicotine Shots.

Typically a 60ml bottle will have 50ml of e-liquid with 10ml of space for you to add a 10ml Nicotine Shot bottle giving you 60ml of 3mg/ml strength. Equally a 120ml bottle will have 100ml of e-liquid with 20ml space for you to add 2x 10ml Nicotine Shot bottles giving you 120ml of 3mg/ml strength.

Nicotine Shot/Shortfill Calculator


As with most nicotine shot or shortfill calculators, they are primarily aimed at working out now much nicotine needs to be added to zero nicotine e-liquid in order to obtain an overall nicotine strength.  There are two ways in which this is achieved; the difference between the two is the final e-liquid amount made.

Nicotine Shot

This is calculated using the amount of zero free e-liquid you have irrespective of the size bottle you are using to make your e-liquid in.

Shortfill

This is calculated using the size of shortfill bottle you have and will work out the amount of nic shot needed to not exceed the shortfill size bottle.

Our Nicotine Shot/Shortfill Calculator will work out both scenarios, giving you the amount of nicotine to add to give you the required strength. Even though I designed the calculator, it’s the best one around so do take a look and do use it!

PG and VG Ratio’s


Where the confusion arises is when you want to know what the final PG/VG ratio of your e-liquid is after you’ve added your nic shot. While in a lot of cases this may not be important to know, there are a few instances where it is important.

Most pod systems are not suited to higher VG levels because of the small coils and wicking ports in the pod. Using an e-liquid greater than 50% VG could clog the wicking ports leading to dry hits and eventually destroying the coil.

Equally, some people will want to know the overall PG/VG ratio of their e-liquid or be able to add a nic shot to bring their PG/VG ratio somewhere close to the level they desire.

When we purchase a shortfill bottle, it will have a PG/VG ratio of the e-liquid inside the shortfill bottle. When adding a nic shot to that bottle, while it will give you the desired overall nic strength, it WILL alter the overall PG/VG ratio.

Because nic shots can be purchased in either VG, PG or a combination of both, we can use the appropriate one to ultimately make the overall PG/VG ratio nearer to that we desire.

Calculation Example Using VG Nic Shots

If we have 50ml of zero nicotine e-liquid with a ratio of 70VG/30PG then we first need to determine the #ml of each base. We do this by the following formula:

Total ml of e-liquid x (VG or PG/100) = ml content. Therefore we have:

50ml x (70/100) = 35ml VG                 50ml x (30/100) = 15ml PG

Now adding a 10ml nic shot suspended in any base will give us a total e-liquid amount of 60ml. If we say in this case the nic shot is suspended in VG, then we simply add the two sums together:

35ml of VG + 10ml VG Nic Shot = 45ml VG               15ml of PG + 0 = 15ml PG

To get back to the new e-liquid PG/VG ratio we now use the reverse formula with the new e-liquid quantity of 60ml:

ml of PG or VG / total e-liquid x 100 = ratio. Therefore we have:

45ml of VG / 60ml of e-liquid x 100 = 75                     15ml of PG / 60ml x 100 = 25

So we can see from the above calculations that 50ml of e-liquid with a ratio of 70VG/30PG ratio with a 10ml VG base nic shot added will give us an overall ratio of 75VG/25PG.

Calculation Example Using PG Nic Shots

If we used a nic shot that was suspended in PG this time, in the same 50ml of zero nicotine e-liquid with a ratio of 70VG/30PG, we would end up with the following:

50ml x (70/100) = 35ml VG                 50ml x (30/100) = 15ml PG

Adding the 10ml nic shot suspended in PG will still give us a total e-liquid amount of 60ml. therefore adding the two sums together:

35ml of VG + 0 = 35ml VG                  15ml of PG + 10ml PG nic shot = 25ml PG

To get back to the new e-liquid PG/VG ratio we now use the reverse formula with the new e-liquid quantity of 60ml:

ml of PG or VG / total e-liquid x 100 = ratio. Therefore we have:

35ml of VG / 60ml of e-liquid x 100 = 58.3                  25ml of PG / 60ml x 100 = 41.7

So we can see from the above calculations that 50ml of e-liquid with a 70VG/30PG ratio with a 10ml PG base nic shot added will give us an overall ratio of 58.3VG/41.7PG.

Calculation Example Using A 50/50 Nic Shots

If we used a nic shot that was suspended in 50VG/50PG this time, in the same 50ml of zero nicotine e-liquid with a ratio of 70VG/30PG, we would end up with the following:

50ml x (70/100) = 35ml VG                 50ml x (30/100) = 15ml PG

Adding the 10ml nic shot suspended in 50/50 will still give us a total e-liquid amount of 60ml. therefore adding the two sums together:

35ml of VG + 5 = 40ml VG                  15ml of PG + 5ml PG nic shot = 20ml PG

To get back to the new e-liquid PG/VG ratio we now use the reverse formula with the new e-liquid quantity of 60ml:

ml of PG or VG / total e-liquid x 100 = ratio. Therefore we have:

40ml of VG / 60ml of e-liquid x 100 = 66.7      20ml of PG / 60ml x 100 = 33.3

So we can see from the above calculations that 50ml of e-liquid with a 70VG/30PG ratio with a 10ml 50/50 base nic shot added will give us an overall ratio of 66.7VG/33.3PG.

To summarise we can see that a shortfill bottle of 50ml of 70VG/30PG with a 10ml nic shot added will give us 60ml with the following e-liquid ratio of:

            VG nic shot:                75VG / 25PG
            PG nic shot:                58.3VG / 41.7PG
            50/50 nic shot:           66.7VG / 33.3PG

Summary

We’ve given 3 examples of the same shortfill bottle size and ratio but adding a nic shot suspended in 3 different base mixes. You can use the same calculations for any size shortfill bottle having any PG/VG ratio and any type of nic shots.

In brief, first multiply the e-liquid amount in your shortfill by one of the PG/VG ratio figures. Divide this figure by 100 and this will give you the quantities in ml of the PG and VG amounts of that e-liquid.

Add the amount in ml of the nic shot you’re adding to your shortfill bottle.

Now divide the combined amount of e-liquid you have by the new figures you have calculated and multiply by 100. This result is the new PG/VG ratio you have in your shortfill bottle after adding a nic shot.

That’s it! You can now work out any PG/VG ratio of the e-liquid you have.

When you want to add nic shots to your e-liquid, use our Nicotine Shot/Shortfill calculator to determine what nicotine strength you want and it will tell you how much nicotine you need to add to achieve that strength. From there you can use what you’ve learnt in this guide to then decide if the nic shot(s) you add are either PG or VG based or some combination of the two.


Hope you found this guide useful and helpful. If you have any questions or feedback, please feel free to leave us a comment below.

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