What Is a Shortfill and How Does Nicotine Calculation Work?

If you are new to DIY e-liquid mixing or have recently started buying shortfill bottles, you might be wondering how much nicotine shot (nicshot) to add. A shortfill is a bottle of nicotine-free e-liquid that is deliberately under-filled to leave room for adding nicotine. Typically, a 50ml shortfill comes in a 60ml bottle, a 100ml shortfill in a 120ml bottle, and so on. This allows vapers to customize their nicotine strength without needing advanced mixing equipment.

Calculating the correct amount of nicshot is essential for achieving your desired nicotine strength while maintaining the right PG/VG balance. In this guide, we explain the shortfill formula, provide quick reference tables, and point you to a handy online calculator.

The Shortfill Formula

The basic formula for calculating how much nicotine shot to add is:

Nicshot Volume (ml) = (Shortfill Volume x Target Strength) / (Nicshot Strength - Target Strength)

Important: Total volume (shortfill + nicshot) must not exceed the bottle capacity. For example, a 50ml shortfill in a 60ml bottle has 10ml of headroom. If your calculation exceeds this, use a higher-strength nicshot or a larger bottle.

Where:

• Shortfill Volume - The amount of nicotine-free e-liquid in the bottle (e.g., 50ml, 100ml)
• Target Strength - The nicotine strength you want to achieve (e.g., 3mg/ml, 6mg/ml)
• Nicshot Strength - The nicotine concentration of your shot (commonly 18mg or 20mg in the UK/EU)

Quick Reference Table: 50ml Shortfill (60ml Bottle)

Quick Reference Table: 100ml Shortfill (120ml Bottle)

A 100ml shortfill in a 120ml bottle has only 20ml of headroom. Most targets above 3mg require more nicshot than the bottle can hold:

Quick Reference Table: 200ml Shortfill (250ml Bottle)

A 200ml shortfill in a 250ml bottle has only 50ml of headroom. Only the 3mg targets fit within the bottle capacity:

PG/VG Ratio After Adding Nicshot

One often overlooked factor is how the nicshot affects your final PG/VG ratio. Most nicotine shots are 100% PG or a high-PG mix (e.g., 50PG/50VG). Adding a PG-based nicshot will increase the PG percentage of your final liquid, which can affect throat hit and vapor production.

Using the Kaser Mods Shortfill Calculator

If you prefer a quick and accurate calculation without doing the math yourself, the Kaser Mods Shortfill Calculator is an excellent online tool. It lets you input your shortfill volume, target nicotine strength, nicshot strength, and PG/VG ratios, then calculates the exact amount of nicshot needed in both millilitres and grams.

The calculator also supports advanced mode for fine-tuning your mix, including:

• Ready to Boost - Quick calculation for standard shortfill sizes
• Longfill - For larger bottles where you add concentrate plus nicotine
• Weight-based measurement - Get results in grams for more accurate mixing by weight

Tips for DIY Shortfill Mixing

• Always use a calculator - Even experienced mixers benefit from accurate calculations. Small errors in nicshot volume can significantly change your final nicotine strength.
• Shake well - After adding the nicshot, shake the bottle thoroughly for 2-3 minutes. Let it sit for a few hours or overnight for the nicotine to fully integrate.
• Steep when needed - While shortfills are pre-steeped by manufacturers, adding nicshot can temporarily mute flavors. Give it 24-48 hours for best results.
• Use the right nicshot - Check whether your nicshot is 100% PG or a PG/VG blend. This affects both throat hit and the final ratio of your liquid.
• Store properly - Keep your shortfill and nicshot in a cool, dark place. Nicotine degrades with heat and UV exposure.

Frequently Asked Questions

What is the difference between shortfill and longfill?

A shortfill is a nicotine-free e-liquid bottle with space left for adding nicshots. A longfill is a larger bottle containing concentrated flavoring that requires both nicotine and a base liquid (PG/VG) to be added. Longfills typically come in 250ml or 500ml bottles and give you more control over the final volume and strength.

Can I mix nicotine shots of different strengths?

Yes, you can combine different nicshot strengths, but the calculation becomes more complex. Using an online calculator like Kaser Mods is recommended for multi-shot mixing.

Why is my shortfill bottle not full after adding the nicshot?

Shortfill bottles are designed with extra headroom specifically for adding nicshots. For a 50ml shortfill in a 60ml bottle, you typically add 10ml of nicshot to reach 60ml total volume at 3mg (using 18mg nicshot). The bottle should be full after the correct nicshot addition.

Is mixing by weight more accurate than by volume?

Yes, mixing by weight is generally more accurate because it is not affected by temperature changes that can alter liquid density. The Kaser Mods calculator provides results in both millilitres and grams for this reason.

Try the Kaser Mods Shortfill Calculator for fast, accurate nicotine calculations every time you mix. For more vaping guides and resources, browse our 2FDeal Vape Blog.