Nic shots are the missing ingredient in a shortfill. A shortfill bottle is deliberately under-filled so you can drop in nicotine yourself and end up with a strength that suits you. The maths is simple once you’ve seen it — and we’ve stuck a calculator on this page so you can stop scribbling on the back of envelopes.
The freebase shot calculator (18 mg)
Use this one when you’re adding our standard 18 mg freebase nic shots to a shortfill.
Work out your final nicotine strength
Each shot is 10 ml at 18 mg/ml. Pick a mode below.
The maths: total nicotine ÷ total volume × 10.
Pick whichever option is closest to what you're after. You can't half-add a shot, so the closest practical strengths sit either side of your target.
The nic salt shot calculator (20 mg)
Use this one when you’re after a smoother throat hit and you’re mixing our 20 mg nic salt shots instead.
Work out your final nicotine strength
Each shot is 10 ml at 20 mg/ml. Pick a mode below.
The maths: total nicotine ÷ total volume × 10.
Pick whichever option is closest to what you're after. You can't half-add a shot, so the closest practical strengths sit either side of your target.
The maths behind it
There’s one formula. That’s it.
Final strength (mg/ml) = (number of shots × 10 × shot strength) ÷ (total volume in ml)
The “× 10” bit is just because each shot is 10 ml. The total volume is the shortfill plus the shots you’ve added together.
Worked example
You’ve got a 50 ml shortfill and you drop in one 18 mg nic shot.
- Shots: 1
- Shot strength: 18 mg/ml
- Shortfill: 50 ml
- Total liquid in the bottle now: 50 + 10 = 60 ml
- Total nicotine: 1 × 10 × 18 = 180 mg
- Final strength: 180 ÷ 60 = 3 mg/ml
Common scenarios
| Shortfill size | Shots added | Shot strength | Final mg/ml |
|---|---|---|---|
| 50 ml | 1 | 18 mg | 3 mg/ml |
| 50 ml | 2 | 18 mg | 5.1 mg/ml |
| 100 ml | 2 | 18 mg | 3 mg/ml |
| 100 ml | 3 | 18 mg | 4.2 mg/ml |
| 50 ml | 1 | 20 mg (salt) | 3.3 mg/ml |
| 50 ml | 2 | 20 mg (salt) | 5.7 mg/ml |
A couple of things worth knowing
- UK law caps nic shots at 10 ml and 20 mg/ml. That’s why our shots come in those sizes — anything bigger or stronger isn’t legal to sell in the UK.
- Shake the bottle properly. Once you’ve added your shot, cap it, shake it, and give it a few minutes. Nicotine isn’t shy, but it does need a hand to mix in.
- You can’t undo it. Add the shot, that’s the strength locked in. Start with one shot if you’re not sure — you can always vape it weaker and top up later.
- Salt vs freebase isn’t about strength, it’s about feel. Salt nic gives a smoother hit at higher strengths, which is why pod kits tend to run on it. Freebase is the classic throat-hit version most sub-ohm vapers stick with.