What Are Longfill E-Liquids and Why Are UK Vapers Switching to Them?
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- A longfill is flavour concentrate, not finished e-liquid. You buy a small bottle of concentrate, add unflavoured base liquid and nicotine, and end up with a much larger finished bottle. Browse the DIY and concentrates range.
- A shortfill is already mixed, a longfill is not. With a shortfill you add two nic shots and go. With a longfill you choose the base, the ratio and the strength. If you are still deciding between formats, read shortfill vs 10ml e-liquid first.
- The appeal is control. You set the VG/PG ratio to suit your kit and the nicotine to suit you, right up to the UK legal maximum of 20mg/ml in the shots you use.
- It usually costs less per ml, because you are paying for flavour rather than for the glycerine, glycol and packaging that make up most of a finished bottle.
- It suits people who vape one or two flavours a lot. If you like a new flavour every week, a 10ml or a shortfill is still the easier buy.
What a longfill e liquid is
A longfill is a part-filled bottle of highly concentrated flavouring. Nothing in it is ready to vape on its own. You buy the concentrate, then add unflavoured base liquid and, if you want it, nicotine, until the bottle is full. The name comes from how much you have to add: a shortfill needs a short top-up, a longfill needs a long one.
The usual shape is a 30ml concentrate in a 120ml bottle, leaving 90ml of space for base and nic shots. That 30ml of flavour is roughly four times the strength of the flavouring in a finished e-liquid, so once it is diluted you get a full 120ml of liquid that tastes the way the mixer intended.
Some concentrates are sold in a plain 30ml dropper bottle instead, with no room to mix in. Those work exactly the same way, you just mix into an empty bottle of your own. Either way, the maths is the same: flavour concentrate typically makes up 10 to 25 per cent of the finished liquid depending on the brand, and everything else is base and nicotine.
How to mix a longfill
Mixing sounds like a job. It is not. Two or three bottles in and it takes about a minute. Here is the order that works.
- 1
Work out your target strength first. Decide how strong you want the finished bottle before you open anything. A 120ml finished liquid at 3mg needs two 18mg nic shots. At 6mg it needs four. Write it down if you are mixing more than one bottle.
- 2
Add the nicotine shots to the concentrate. Pull the nib out of the longfill bottle, pour the shots in, and put the nib back. Adding nicotine before base means it disperses through the thickest part of the mix.
- 3
Top up with unflavoured base in the ratio your kit wants. Fill to the shoulder of the bottle, not the brim, or you will have nowhere for the liquid to move when you shake it.
- 4
Shake properly, for two minutes. Turn the bottle end over end rather than rattling it. Concentrate is thick and it will sit in a layer at the bottom if you rush this.
- 5
Steep if the flavour calls for it. Fruits and menthols are usually fine straight away. Custards, tobaccos and cream flavours want a few days in a cool, dark cupboard with a shake each day.
- 6
Label the bottle. Flavour name, strength, date mixed. Three unlabelled bottles in a drawer all look identical, and guessing the strength of one is a bad way to start a morning.
Longfill vs shortfill vs 10ml
These are the three ways to buy e-liquid in the UK and they sit on a straight line: the less work you do, the more you pay per ml and the less say you have in the result.
| Feature | Longfill | Shortfill | 10ml |
|---|---|---|---|
| What you buy | Flavour concentrate only | Finished liquid, 0mg | Finished liquid with nicotine |
| Mixing needed | Base plus nic shots | Nic shots only | None |
| Flavour strength | You set it | Fixed by the maker | Fixed by the maker |
| VG/PG ratio | You set it | Fixed, usually 70/30 | Fixed, usually 50/50 |
| Max strength | Whatever the shots allow | About 3mg to 6mg | Up to 20mg/ml |
| Cost per ml | Lowest | Middle | Highest |
| Convenience | Lowest | Good | Highest |
| Packaging waste | Least | Moderate | Most |
The 10ml bottle is the only one of the three that arrives ready to vape at a real strength, because UK law limits nicotine-containing bottles to 10ml and 20mg/ml. That is why pod-kit users on 10mg or 20mg salts stay with 10mls. A shortfill is the middle ground, and a longfill is the version for people who want to decide everything themselves.
30ml
of concentrate in the typical longfill
120ml
of finished liquid once mixed
2
18mg nic shots to take 120ml to 3mg
Is a longfill really cheaper?
At the checkout, a longfill looks like a worse deal. You are buying a small bottle, and you still need base liquid and nic shots on top. The saving only appears once you divide by the volume you end up with.
Most of a finished e-liquid, by volume, is vegetable glycerine and propylene glycol. Those are cheap. What you pay a premium for is flavour, the bottle, the box and the shipping of a heavy 100ml container. A longfill strips out almost all of that: you pay for the flavour and move a small parcel, then supply the bulk yourself. Buy base liquid in a litre and the cost per ml of the finished bottle drops well below anything pre-mixed.
The other saving is the one nobody counts: liquid you do not throw away. If a flavour is too sweet or not cold enough, you can fix the next batch instead of writing off 100ml of something you do not enjoy.
One thing that does not change is tax. From 1 October 2026 the Vaping Products Duty adds £2.20 per 10ml plus VAT to e-liquid, nicotine or not, which is £2.64 on every 10ml at the till. Because the duty is flat per ml, it lands on base liquid and nic shots just as it lands on a finished bottle, so it narrows the gap between formats in percentage terms without changing the order. Stock held before 1 October can be sold at pre-duty prices until 31 March 2027.
Flavours worth starting with
Fruit and menthol concentrates are the easiest first mixes because they need little or no steeping, so you find out quickly whether you have got the dilution right. Desserts and creams are the ones that reward patience. These are the profiles that sell steadily.
Red Astaire by T-Juice
Bitter grape, sweet mixed berries and floral aniseed, with a cooling menthol and eucalyptus finish. It is probably the most recognisable UK mix there is, and it is a good first concentrate because it is forgiving: a little under-diluted and it is just bolder, rather than unpleasant. Vapeable straight after mixing, better after two or three days.
Profile: grape, mixed berries, aniseed, menthol and eucalyptus. Format: 30ml concentrate. Steep: 2 to 3 days.
Vamp Toes by Vampire Vape
Juicy mixed berries with a bold aniseed note sitting underneath them, which is what stops it reading as plain sweet fruit. There is no ice in this one at all, so it is the pick if you want a berry all-day vape without the cold, and the aniseed gives you something to aim at when you are deciding how far to dilute it. The bottle asks for 15 to 20 per cent, same as the rest of the range.
Profile: mixed berries, aniseed, no ice. Format: 30ml concentrate. Steep: vapeable straight away, better after a day or two.
Blue Raspberry Ice by Zeus Juice
Ripe blue raspberry with an ice-cold kick on the exhale, which is what stops it reading as plain sweet fruit. The tang and the cooling arrive together, so it is the pick if you want cold in the mix without going to a straight menthol. The bottle recommends 15 to 20 per cent, so start at the low end and add more if you want it louder.
Profile: blue raspberry, ice. Format: 30ml concentrate. Steep: vapeable straight away, better after a day or two.
Migos Moon by Nasty Ballin
Juicy orange with a tart lemonade edge. This is the citrus pick, and it is a good demonstration of why people mix their own: citrus can turn sharp if it is too strong, so being able to run it slightly thinner than the label suggests makes a real difference. No ice in the description.
Profile: orange, lemonade, no ice listed. Format: 30ml concentrate. Steep: vapeable straight away, better after a day or two.
Creme Kong by Joe’s Juice
A creamy custard biscuit dunked in a fresh brew, which is how the makers put it and it is a fair summary: vanilla custard, a biscuit base and a rounded tea note behind both. Dessert concentrates are where steeping matters most: mixed today it tastes flat and slightly chemical, and a week later it is rounded and creamy. Mix it, put it at the back of the cupboard and forget about it. Strawberry Creme Kong from the same range behaves the same way if you want fruit with the cream.
Profile: vanilla custard, biscuit, tea. Format: 30ml concentrate. Steep: 7 days or more.
A note on percentages: every concentrate has a recommended mixing percentage, usually printed on the bottle or on the product page, and they are not all the same. A 20 per cent fruit and a 10 per cent dessert are both normal. Follow the bottle rather than a rule of thumb, at least until you know the brand.
Match the base and nicotine to your kit
This is the step people get wrong, and it is the one that makes longfills worth the effort when you get it right. The concentrate does not care what kit you own. The base liquid does.
Pod kit or MTL tank
Coils of 0.8Ω and above want a 50/50 base and a 50VG shot. Use a 50VG nic salt shot if you want a smoother throat hit at a higher strength.
Sub-ohm tank or mod
Coils below 0.5Ω want a 70/30 base and a matching 70VG 18mg shot, at 3mg to 6mg finished. Thicker liquid, more vapour, gentler hit.
Mixing a thin 50/50 base into a bottle you then vape in a sub-ohm tank is the usual cause of a flooded coil and liquid in your mouth. Going the other way, a 70/30 base in a small pod coil will wick too slowly and burn. If leaks are already a familiar problem, the fixes in our guide to filling a pod kit correctly apply to home-mixed liquid exactly as they do to a shop bottle.
On strength, remember what the format can and cannot do. Two 18mg shots in 120ml gives roughly 3mg. To reach 10mg or 20mg in a big bottle you would need so many shots that there would be no room for the base, which is why high-strength vapers stay on 10ml salts and use longfills for their lower-strength, higher-volume vaping.
Steeping, storage and shelf life
Steeping is just time. The flavour compounds, the base and the nicotine need a while to settle into each other, and some flavours need longer than others. Fruits and menthols are usually good immediately. Berries and mixed fruits improve over a couple of days. Custards, creams, tobaccos and bakery flavours want a week, sometimes two.
There is no trick that beats leaving it alone. Warm water baths and ultrasonic cleaners get talked about a lot and mostly just risk cooking the flavour. Shake the bottle once a day, keep it somewhere cool and dark, and taste it at day three and day seven.
Unmixed concentrate keeps far longer than finished liquid, which is part of the appeal if you buy a few at once. Once mixed, treat it like any other bottle: upright, capped, away from sunlight and radiators, and plan on three to six months at full quality. Our guide to e-liquid shelf life and storage covers what darkening actually means and when a bottle is genuinely past it.
If you are mixing 120ml at a time, it is also worth knowing roughly how long that will last you. Our breakdown of how long 100ml of e-liquid lasts gives usable figures for pod and sub-ohm users, and the same maths applies here.
Should you switch?
Longfills suit you if you already know what you like. If you have been vaping the same berry ice or the same custard for months, buying concentrate and base is straightforwardly cheaper and gives you a bottle tuned to your kit rather than to the average buyer’s.
They suit you less if flavour variety is the point. Mixing five different concentrates means five bottles on the go, five steeping times and a lot of labelling. In that case a ready-made shortfill is doing real work for you.
Beginners are often told longfills are advanced. They are not, really. The only genuinely new skills are reading a mixing percentage and being patient with a dessert flavour. What does trip people up is trying it while also learning a new device, which is one of the common mistakes new vapers make. Get comfortable with your kit and a shortfill first, then move across once you know which flavour you want a lot of.
Pre-duty prices until 31 March 2027
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Quick answers
How is a longfill different from a shortfill?
A shortfill is finished, nicotine-free e-liquid with a little space left for nic shots. A longfill is flavour concentrate only, so you add both base liquid and nicotine. A shortfill needs a short top-up, a longfill needs a long one.
Are longfills cheaper than buying finished bottles?
Per ml of finished liquid, yes, usually clearly so. The concentrate costs more than it looks per bottle, but you are supplying the bulk yourself, and base liquid bought in volume is the cheapest part of any e-liquid.
Do longfills need steeping?
It depends on the flavour. Fruits and menthols are generally ready straight after a good shake. Custards, creams, bakery and tobacco flavours are much better after a week in a cool, dark cupboard.
Can I vape a longfill without diluting it?
No. Undiluted concentrate is several times too strong, tastes harsh and will gunk a coil quickly. Mixing is not optional with this format.
What strength can I mix a longfill to?
Realistically 3mg to 6mg. Two 18mg shots in 120ml gives about 3mg, four gives about 6mg. High-strength vapers who want 10mg or 20mg are better served by 10ml nic salts.
Are longfills suitable for beginners?
Yes, once you are settled with your kit. The mixing itself takes a minute and the bottle tells you the percentage to use. Most people find it easy by the second or third batch.
