Use this longfill calculator to figure out exactly how much nicotine base, VG, and PG to add to your bottle. This calculator assumes your flavor concentrate is PG-based (the standard for most longfills).
Tip: If your target VG is impossible with your flavor and nic settings, the calculator will show the closest achievable mix.
What is a longfill calculator?
A longfill calculator helps you complete an e-liquid mix when you buy a bottle that already contains flavor concentrate, but still needs nicotine and base liquid. Longfills are popular because they make mixing easier: the flavoring is pre-measured, and you only add what is missing.
The challenge is simple but important: if you add too much nicotine base, you can overshoot your bottle volume. If you add the wrong amount of PG or VG, your final ratio may feel too harsh, too thin, or too thick for your device. A calculator removes guesswork and gives you repeatable results.
How this longfill calculator works
1) Nicotine volume
First, the tool calculates how much nicotine base is needed to hit your target strength: target nicotine (mg/ml) × final volume (ml) ÷ nicotine shot strength (mg/ml). That gives the exact milliliters of nicotine base to add.
2) Remaining space in the bottle
Next, it subtracts flavor concentrate and nicotine volume from your final bottle size. What remains is the plain base you still need to add.
3) PG/VG balancing
The calculator assumes flavor concentrate is PG-based. It also uses the VG percentage you entered for your nicotine shot. From there, it computes the extra VG and PG required to reach your desired final VG ratio. If that exact ratio cannot be reached, it gives you the closest practical result.
Step-by-step guide to using the calculator
- Enter the final size of your bottle (for example, 60 ml or 120 ml).
- Enter how much flavor is already inside the longfill bottle.
- Set your target nicotine strength (such as 3 mg/ml).
- Enter nicotine shot strength and shot bottle size from the label.
- Set shot VG percentage and your desired final VG ratio.
- Click Calculate Mix and follow the amounts shown.
Example mix (quick practical scenario)
Suppose you have a 120 ml longfill with 30 ml flavor concentrate, and you want 3 mg/ml nicotine. You are using 20 mg/ml nicotine shots (10 ml each), and you want around 70VG/30PG. The calculator returns the nicotine volume first, then tells you the exact VG and PG to complete the bottle.
This is much more reliable than “adding one or two shots and topping off” because it keeps nicotine strength and viscosity aligned. That matters for both flavor consistency and coil performance.
Common mistakes this tool helps you avoid
- Overfilling the bottle: especially when chasing higher nicotine levels.
- Wrong nicotine strength: from estimating shot counts without volume math.
- Poor VG/PG ratio: leading to leaking, dry hits, or muted flavor.
- Inconsistent batches: when each refill is mixed slightly differently.
Longfill safety and best practices
Mix safely
Nicotine is a toxic substance at high concentrations. Wear gloves, avoid skin contact, and clean spills immediately. Keep all mixing supplies away from children and pets.
Label every bottle
Always record nicotine strength, VG/PG ratio, flavor name, and mix date. Good labeling prevents confusion and helps you repeat successful mixes.
Let your liquid steep if needed
Some flavor profiles (especially creams, custards, and bakery blends) improve after resting. Fruit or menthol profiles are often shake-and-vape, but a short steep can still smooth the mix.
FAQ
Can I use nicotine salts with this calculator?
Yes. Just enter the actual strength and VG percentage of your salt shot.
What if my flavor concentrate is not PG-based?
This tool assumes PG-based flavoring, which is standard. If yours is different, treat the result as an estimate and adjust manually.
Why can’t I always hit my exact target VG?
Flavor concentrate and nicotine base already contribute PG and/or VG. Sometimes those fixed inputs make your target ratio physically impossible. In that case, the calculator gives the closest achievable blend.
Bottom line
A good longfill calculator saves time, improves consistency, and helps you avoid costly errors. If you mix regularly, using a calculator should be your standard workflow—not an optional step.