How to Mix Nic Shots Into Shortfill E-Liquid: Maths and Method

• A nic shot is 10ml of unflavoured nicotine liquid, usually 18mg/ml or 20mg/ml (20mg/ml is the UK legal maximum for a nicotine bottle).
• 50ml shortfill plus one 18mg shot makes 60ml at 3mg. That is what the empty space in a 60ml shortfill bottle is designed for.
• 100ml shortfill plus two 18mg shots makes 120ml at 3mg. Two 20mg shots give about 3.3mg instead.
• The formula is simple: shot strength times shot volume, divided by the finished volume, gives your final mg/ml.
• Shake hard, then rest it. A minute of shaking mixes it; a few hours to a day lets the flavour settle back.

Why shortfills need a nic shot at all

UK rules cap any bottle of nicotine-containing e-liquid at 10ml and 20mg/ml. Anything bigger, such as a 50ml or 100ml bottle, can only be sold as 0mg. Manufacturers get round this by selling the flavoured liquid “short” of the bottle’s full capacity, so a 50ml shortfill usually arrives in a 60ml bottle and a 100ml shortfill in a 120ml bottle. The space at the top is there for you to add nicotine yourself. That is where the name comes from. If you want the background, our guide to why e-liquid bottles are 10ml in the UK covers the rules.

A nic shot, sometimes called a nicotine booster, is a 10ml bottle of unflavoured liquid containing nicotine at 18mg/ml or 20mg/ml. It exists purely to be poured into a shortfill. A plain shot adds no taste of its own, but the extra 10ml of base dilutes the flavour slightly. If you vape shortfill e-liquid with nicotine, you need shots; if you vape at 0mg, you can use the shortfill exactly as it comes.

Shortfills are made for sub-ohm tanks and larger kits, where the finished strength is usually low: 3mg is the most common, and 6mg is about the ceiling for direct-lung vaping. If you want 10mg or 20mg for a tight mouth-to-lung pod, a ready-made nic salt is the easier route than trying to force strength into a shortfill.

The maths: how strong your mix will be

There is one formula and it covers every combination. Multiply the shot strength by the amount of shot you add to get the total nicotine in milligrams, then divide by the finished volume in the bottle.

Final strength (mg/ml) = shot strength x shot volume / (shortfill volume + shot volume)

So one 10ml shot at 18mg/ml holds 180mg of nicotine. Poured into 50ml of shortfill, that 180mg is spread across 60ml, which is 3mg/ml. Two 18mg shots hold 360mg; in 100ml of shortfill that is 360mg across 120ml, again 3mg/ml. Because you are always diluting a shot of 20mg/ml or less, the finished liquid can never be stronger than the shot you started with. It is always far weaker.

Figures are rounded to one decimal place. The highlighted rows are the standard combinations the bottles are built for. Anything else needs either a bigger empty bottle or an odd amount of shot measured out, which is where the formula earns its keep.

Getting 6mg or another custom strength

Work the formula backwards. Decide the strength and finished volume you want, multiply them to get the milligrams of nicotine needed, then divide by the shot strength to get the millilitres of shot.

Example: 6mg from a 50ml shortfill using 18mg shots. If you add x ml of shot, you need 18 x x / (50 + x) = 6. Solving that gives x = 25ml, so two and a half shots, and a finished volume of 75ml at 6mg/ml. A 60ml shortfill bottle will not hold that, so decant into a larger empty bottle first. Measure the half shot with a syringe rather than guessing.

Example: something between 3mg and 6mg. Two 18mg shots in a 50ml shortfill, decanted into a bigger bottle, gives 70ml at about 5.1mg. That is a common middle ground for people who find 3mg a touch light in a sub-ohm tank.

Example: under 3mg. One 18mg shot in a 100ml shortfill gives 110ml at about 1.6mg, and the bottle has room to spare.

For help picking the number in the first place, our nicotine strength guide sets out typical strengths by habit and device. As a rule, shortfills belong in sub-ohm kits at low strengths; never put 18mg or 20mg liquid in a sub-ohm kit.

Choosing the right nic shot

Shots differ in three ways: strength, PG/VG ratio and whether they are freebase or nicotine salt. Strength is covered above. The ratio matters because a 10ml shot is roughly a sixth of a 60ml bottle, so it pulls the finished ratio towards its own.

Most shortfills are 70/30 VG/PG. Add a 50/50 shot to 50ml of 70/30 and the finished 60ml works out at about 67% VG. Add a 70VG shot and it stays at 70/30. For most tanks the difference is small, but if you like a thick cloud-focused liquid or your coil is prone to leaking, match the shot to the shortfill. Our guide to PG/VG ratios explains what each ratio does.

Nic salt shots give a smoother feel at the same strength, which some people prefer in a warmer sub-ohm set-up. Freebase shots give a sharper throat hit. Neither changes the maths. A few examples from our nic shots range:

• Nic Nic Nicotine Shot 10ml 18mg 50VG: a plain freebase shot for 50/50 or 70/30 shortfills.
• Nic Nic Nicotine Shot 10ml 15mg/18mg 70VG: keeps a 70/30 shortfill at 70/30.
• Salt Nicotine Shot 10ml 18mg 50VG: a salt-based shot for a smoother finish.
• Nic Nic Nicotine Salt 10ml 20mg 50VG: a 20mg salt shot, which lands at about 3.3mg in 60ml.
• Zeus Juice Nicotine Shot 10ml 18mg 70VG: a high-VG shot for sub-ohm liquids.

Some shots are sold as “ice” or “cool” shots with a cooling agent added. They work the same way for strength but will add a chill to whatever flavour you pour them into, so treat them as a flavour choice as well as a nicotine one.

How to add a nic shot in six steps

This takes about two minutes, plus resting time. Do it on a clear, flat surface away from children and pets, with a sheet of kitchen roll underneath.

1. 1
   Check the bottle has room. Read the label: a 50ml in a 60ml bottle takes one shot, a 100ml in a 120ml bottle takes two. If you want more shot than that, decant into a larger empty bottle first.
2. 2
   Remove the nozzle. Most shortfill tips pull off with a firm tug, or twist off on some brands. Pulling it with a bit of kitchen roll gives you grip and catches drips.
3. 3
   Pour in the shot. Squeeze the whole 10ml shot into the open neck. For part-shots, measure with a clean syringe. Go slowly so it does not overflow.
4. 4
   Refit the nozzle and cap. Push the tip back until it seats fully, then screw the child-resistant cap on tight.
5. 5
   Shake for one to two minutes. Nicotine base is thinner than most shortfills and sits in a layer if you do not mix it properly. Shake hard, then turn the bottle upside down a few times.
6. 6
   Let it settle, then label it. Leave it a few hours, or overnight, so the bubbles clear and the flavour evens out. Write the strength on the bottle so nobody picks it up thinking it is 0mg.

If the flavour seems slightly muted after adding a shot, give it a day. The extra base blends in and the flavour usually comes back. Our guide on how steeping changes flavour explains why resting time helps.

Mistakes that spoil a mix

Two other habits make a difference. First, keep shots and mixed bottles in a cool, dark cupboard out of reach of children; nicotine liquid is harmful if swallowed, and our guide on what happens if you swallow e-liquid explains what to do. Wipe any spill off your skin with soap and water. Second, mind the ratio. If your tank starts gurgling after a new mix, check the coil and the fill before blaming the shot; see how to stop e-liquid leaks.

Storage is the same as for any e-liquid: capped, upright, out of the sun. Mixed bottles keep as well as the shortfill did before you opened it.

Shortfill plus shot, or 10ml bottles?

From 1 October 2026 Vaping Products Duty applies at £2.20 per 10ml, or £2.64 with VAT, on every vaping liquid whether it contains nicotine or not. That means a shortfill and its shots carry duty on every millilitre, just like a 10ml bottle. A finished 60ml mix carries £15.84 of duty with VAT and a finished 120ml carries £31.68. The duty is the same per ml on every format, so it neither widens nor narrows any gap between them. Our article on how much vape prices will go up has the full breakdown. Pre-duty stock is on sale until 31 March 2027.

The real choice is about your device. A shortfill plus shot gives you a big bottle at a low strength, ideal for a sub-ohm tank. 10ml e-liquids and nic salts come ready-mixed at higher strengths, ideal for pods. If you are weighing the two, our guide to shortfill vs 10ml e-liquid compares them side by side. If you want even more control, longfills let you add both base and shots to a concentrate.

Everything you need for the perfect mix

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