Nicotine shot: getting the dose right
You have the shortfill open on the table, the headroom staring back at you, and one small clear bottle left to deal with. That is where a lot of home mixes go sideways, somewhere between a rough guess and a strength that matches nothing on the label. Dosing a nicotine shot is not difficult, though. A single formula covers every bottle size sold in Britain, and it takes about a minute to learn properly.
How much nicotine shot goes into a shortfill
A nicotine shot sold in the United Kingdom is a 10 ml bottle of unflavoured liquid, usually at 18 mg/ml or 20 mg/ml, twenty being the legal ceiling for nicotine containing e-liquid here. That format exists because British rules cap nicotine bottles at 10 ml, so the nicotine arrives separately from the flavour.
The British shortfill system is built around exactly that. A 50 ml shortfill is supplied in a 60 ml bottle, and a 100 ml shortfill in a 120 ml bottle. The empty headroom is not a packaging accident, it is sized for one or two shots.
The formula is short. Final strength in mg/ml equals the total volume of shots multiplied by the shot strength, divided by the final volume of the bottle.
Turn it around and it gives you the volume to add: shot volume equals the target strength multiplied by the final volume, divided by the strength of the shot. A 10 ml shot at 18 mg/ml poured into a 50 ml shortfill gives 180 mg spread across 60 ml, which lands at 3 mg/ml.
Working the sum through, step by step
The formula stays abstract until you apply it to a real bottle. Breaking the calculation down makes the logic obvious and frees you from any online calculator.
Every 10 ml shot carries a fixed quantity of nicotine. At 18 mg/ml it holds 180 mg in total, at 20 mg/ml it holds 200 mg. Diluting that fixed quantity into the finished volume is what sets the strength, and nothing else does.
Two shots of 18 mg dropped into a 100 ml shortfill give 360 mg across 120 ml, so the result is the same 3 mg/ml as the smaller bottle. This is why the two shortfill formats behave identically once mixed, a point British listings rarely bother to explain.
Mixing from scratch works the same way, except that you also have to subtract. Say you want 100 ml at 6 mg/ml with 20 mg shots. You need 600 mg, so 30 ml of shots, which occupy 30 ml of the bottle. With 12 ml of flavour concentrate on top, the base liquid fills the remaining 58 ml and the total lands exactly on 100 ml.
A dosage table you can check
The table below applies the formula to the combinations you meet most often on British shelves. Every line can be reproduced with the calculation above.
| Final volume | Shot strength | Shots of 10 ml | Volume of shots | Final strength |
|---|---|---|---|---|
| 60 ml (50 ml shortfill) | 18 mg/ml | 1 | 10 ml | 3 mg/ml |
| 60 ml (50 ml shortfill) | 20 mg/ml | 1 | 10 ml | 3.3 mg/ml |
| 120 ml (100 ml shortfill) | 18 mg/ml | 2 | 20 ml | 3 mg/ml |
| 120 ml (100 ml shortfill) | 20 mg/ml | 2 | 20 ml | 3.3 mg/ml |
| 100 ml mixed from scratch | 20 mg/ml | 3 | 30 ml | 6 mg/ml |
| 50 ml mixed from scratch | 20 mg/ml | 1.5 | 15 ml | 6 mg/ml |
Notice that the shortfill lines never reach a round number when you use 20 mg shots. That slight offset is normal and it is the reason a good many British suppliers keep 18 mg shots in stock alongside the 20 mg ones.
What a nicotine shot does to your PG VG ratio
Here is the detail the calculators leave out. A nicotine shot is not a volume neutral ingredient. It takes up a real share of the bottle, and it carries a PG VG ratio of its own.
British shots are commonly sold at 50/50, at 70/30 and occasionally at 100 percent PG, and the listing states it. On a heavily nicotined mix from scratch, the shots can account for a third of the total volume, which drags the finished blend towards PG and sharpens the throat sensation.
That shift matters if you were aiming for a thick, VG heavy liquid. The usual answer is to start from a base a few points richer in VG than the result you want, a mechanism covered in our guide to the PG VG ratio of a DIY base. Salt based shots exist too and behave differently in the mouth at the same figure, which we compare in our piece on nic salts and freebase.
Shortfills, longfills and mixing from scratch
Three routes lead to the same bottle in Britain, and the arithmetic never changes between them. Only the amount of work does.
The shortfill is the quickest. The flavour is already diluted in the base, you add the shot, you cap and you shake. The longfill sits in the middle: a small volume of concentrate arrives in a large empty bottle, and you top it up with base liquid and shots yourself.
Mixing from scratch gives you every variable, including the ratio and the flavour percentage, and it is the route described in our complete method for making your own e-liquid. It is also the only one where forgetting to deduct the volume of the shots will overflow the bottle.
Handling, storage and the mistakes that spoil a batch
A failed mix rarely comes from the formula. It comes from how the formula is applied, and three slips account for most of them.
The first is forgetting to subtract the volume of the shots from the base liquid, which either overfills the bottle or throws the strength off. The second is confusing the strength of the shot, 18 or 20 mg/ml, with the final strength of the liquid, which is a far smaller number. The third is treating nicotine as an ordinary ingredient.
It is not one. Wear gloves when you handle it, keep the bottles well out of reach of children and pets, and store them upright, capped, away from light and heat. Label every bottle you fill with its contents and the date, because an unmarked bottle in a drawer is the classic accident waiting to happen. None of these products are for sale to anyone under eighteen in the United Kingdom.
Frequently asked questions
Can I mix a DIY e-liquid without any nicotine at all?
Yes. Replace the volume of the shots with plain base liquid and the rest of the recipe is unchanged. A shortfill left as it comes is already exactly that, a nicotine free bottle.
What happens if I add one shot too many?
The final strength rises and the throat sensation becomes harsh. The fix is to lengthen the mix with more base liquid to dilute it back down, then recalculate the flavour percentage across the new volume.
Are shots sold at strengths other than 18 and 20 mg/ml?
Twenty is the legal maximum in Britain for nicotine containing e-liquid, and 18 is the other common figure. Lower strengths turn up occasionally, and the formula works unchanged once you swap in the real number from the bottle.
Should the shot go in before or after the flavour concentrate?
The order makes no difference to the finished liquid. Most people pour the base first, then the shots, then the concentrate, simply because it is easier to measure small volumes last.
How long does an unopened nicotine shot keep?
Nicotine oxidises over time when exposed to air, heat and light, and the liquid may darken. Keep the bottles cool, dark and firmly capped, and close them carefully after each use.
What to remember about dosing your shots
There is no mystery to a nicotine shot. One formula, one final volume, one target strength, and the sum comes out. Remembering that a 10 ml shot carries either 180 or 200 mg of nicotine is enough to improvise any calculation without a tool in front of you.
The rest is discipline: subtract the volume you add, read the strength on the bottle rather than assuming it, and store everything properly. That discipline is exactly what separates a repeatable house recipe from a bottle you can never make twice, whichever route to the final mix you take.
Editorial content for adult readers only. Nicotine is an addictive substance and vaping products are not for sale to under-18s in the United Kingdom. This article is not a buying recommendation.
